From 3538a6642dbfe2aebc90e721915bc86ea343f3e6 Mon Sep 17 00:00:00 2001
From: Ojasva Jain <44553464+ojasva@users.noreply.github.com>
Date: Mon, 4 Oct 2021 02:04:18 +0530
Subject: [PATCH 1/8] Hill Cipher Implementation in JAVA

---
 Ciphers/HillCipher.java | 172 ++++++++++++++++++++++++++++++++++++++++
 1 file changed, 172 insertions(+)
 create mode 100644 Ciphers/HillCipher.java

diff --git a/Ciphers/HillCipher.java b/Ciphers/HillCipher.java
new file mode 100644
index 000000000000..0a3b50308d21
--- /dev/null
+++ b/Ciphers/HillCipher.java
@@ -0,0 +1,172 @@
+package Ciphers;
+
+import java.util.*;
+
+/*
+* Java Implementation of Hill Cipher
+* Hill cipher is a polyalphabetic substitution cipher. Each letter is represented by a number belonging to the set Z26 where A=0 , B=1, ..... Z=25.
+* To encrypt a message, each block of n letters (since matrix size is n x n) is multiplied by an invertible n × n matrix, against modulus 26.
+* To decrypt the message, each block is multiplied by the inverse of the matrix used for encryption.
+* The cipher key and plaintext/ciphertext are user inputs.
+* @author Ojasva Jain
+*/
+
+public class HillCipher{
+static Scanner in = new Scanner (System.in);
+
+/* Following function encrypts the message
+*/
+static void encrypt(String message)
+{
+    message = message.toUpperCase();
+    // Get key matrix
+    System.out.println("Enter key matrix size");
+    int n = in.nextInt();
+    System.out.println("Enter Key/encryptionKey matrix ");
+    int keyMatrix[][] = new int [n][n];
+    for(int i=0;i<n;i++){
+        for(int j=0;j<n;j++){
+            keyMatrix[i][j] = in.nextInt();
+        }
+    }
+    //check if det = 0
+    if(determinant(keyMatrix,n)%26 == 0)
+    {
+        System.out.println("Invalid key, as determinant = 0. Program Terminated");
+        return;
+    }
+
+    int [][]messageVector = new int[n][1];
+    String CipherText="";
+    int cipherMatrix [][] = new int [n][1];
+    int j = 0;
+    while(j<message.length()){
+    for (int i = 0; i < n; i++){
+        if(j>=message.length()){ messageVector[i][0] = 23;}
+        else
+        messageVector[i][0] = (message.charAt(j))%65;
+        System.out.println(messageVector[i][0]);
+        j++; 
+    }
+    int x, i;
+    for (i = 0; i < n; i++)
+    {
+        cipherMatrix[i][0] = 0;
+
+            for (x = 0; x < n; x++)
+            {
+                cipherMatrix[i][0] += keyMatrix[i][x] * messageVector[x][0];
+            }
+            System.out.println(cipherMatrix[i][0]);
+            cipherMatrix[i][0] = cipherMatrix[i][0] % 26;
+        }
+    for (i = 0; i < n; i++)
+    CipherText += (char)(cipherMatrix[i][0] + 65);
+}
+System.out.println("Ciphertext: "+ CipherText);
+}
+//Following function decrypts a message
+static void decrypt(String message)
+{
+    message = message.toUpperCase();
+    // Get key matrix
+    System.out.println("Enter key matrix size");
+    int n = in.nextInt();
+    System.out.println("Enter inverseKey/decryptionKey matrix ");
+    int keyMatrix[][] = new int [n][n];
+    for(int i=0;i<n;i++){
+        for(int j=0;j<n;j++){
+            keyMatrix[i][j] = in.nextInt();
+        }
+    }
+    //check if det = 0
+    if(determinant(keyMatrix,n)%26 == 0)
+    {
+        System.out.println("Invalid key, as determinant = 0. Program Terminated");
+        return;
+    }
+    //solving for the required plaintext message
+    int [][]messageVector = new int[n][1];
+    String PlainText="";
+    int plainMatrix [][] = new int [n][1];
+    int j = 0;
+    while(j<message.length()){
+        for (int i = 0; i < n; i++){
+            if(j>=message.length()){ messageVector[i][0] = 23;}
+            else
+            messageVector[i][0] = (message.charAt(j))%65;
+            System.out.println(messageVector[i][0]);
+            j++; 
+        }
+        int x, i;
+        for (i = 0; i < n; i++)
+        {
+            plainMatrix[i][0] = 0;
+    
+                for (x = 0; x < n; x++)
+                {
+                    plainMatrix[i][0] += keyMatrix[i][x] * messageVector[x][0];
+                }
+    
+                plainMatrix[i][0] = plainMatrix[i][0] % 26;
+            }
+        for (i = 0; i < n; i++)
+        PlainText += (char)(plainMatrix[i][0] + 65);
+    }
+    System.out.println("Plaintext: "+PlainText);
+}
+
+// Determinant calculator
+public static int determinant(int a[][], int n){
+    int det = 0, sign = 1, p = 0, q = 0;
+
+    if(n==1){
+        det = a[0][0];
+    }
+    else{
+        int b[][] = new int[n-1][n-1];
+        for(int x = 0 ; x < n ; x++){
+            p=0;q=0;
+            for(int i = 1;i < n; i++){
+                for(int j = 0; j < n;j++){
+                    if(j != x){
+                        b[p][q++] = a[i][j];
+                        if(q % (n-1) == 0){
+                            p++;
+                            q=0;
+                        }
+                    }
+                }
+            }
+            det = det + a[0][x] *determinant(b, n-1) * sign;
+            sign = -sign;
+        }
+    }
+    return det;
+}
+
+// Function to implement Hill Cipher
+static void hillcipher(String message)
+{
+    message.toUpperCase();
+    System.out.println("What do you want to process from the message?");
+    System.out.println("Press 1: To Encrypt");
+    System.out.println("Press 2: To Decrypt");
+    short sc = in.nextShort();
+    if(sc == 1)
+    encrypt(message);
+    else if(sc == 2)
+    decrypt(message);
+    else
+    System.out.println("Invalid input, program terminated.");
+}
+
+// Driver code
+public static void main(String[] args)
+   {
+    // Get the message to be encrypted
+    System.out.println("Enter message");
+    String message = in.nextLine();
+    hillcipher(message);
+    }
+}

From 4e6878ebc66253d797eed4b900d8a992b7f407b0 Mon Sep 17 00:00:00 2001
From: Ojasva Jain <44553464+ojasva@users.noreply.github.com>
Date: Tue, 5 Oct 2021 01:18:42 +0530
Subject: [PATCH 2/8] Determinant of a Matrix

---
 Maths/DeterminantOfMatrix.java | 61 ++++++++++++++++++++++++++++++++++
 1 file changed, 61 insertions(+)
 create mode 100644 Maths/DeterminantOfMatrix.java

diff --git a/Maths/DeterminantOfMatrix.java b/Maths/DeterminantOfMatrix.java
new file mode 100644
index 000000000000..f5ed09ca167d
--- /dev/null
+++ b/Maths/DeterminantOfMatrix.java
@@ -0,0 +1,61 @@
+package Maths;
+import java.util.*;
+
+/* 
+* @author Ojasva Jain
+* Determinant of Matrix Wikipedia link : https://en.wikipedia.org/wiki/Determinant
+*/
+public class DeterminantOfMatrix
+{
+    // Determinant calculator
+    //@return determinant of the input matrix
+    static int determinant(int a[][], int n)
+    {
+        int det = 0, sign = 1, p = 0, q = 0;
+        if(n==1)
+        {
+            det = a[0][0];
+        }
+        else
+        {
+            int b[][] = new int[n-1][n-1];
+            for(int x = 0 ; x < n ; x++)
+            {
+                p=0;q=0;
+                for(int i = 1;i < n; i++)
+                {
+                    for(int j = 0; j < n;j++)
+                    {
+                        if(j != x)
+                        {
+                            b[p][q++] = a[i][j];
+                            if(q % (n-1) == 0)
+                            {
+                                p++;
+                                q=0;
+                            }
+                        }
+                    }
+                }
+                det = det + a[0][x] *determinant(b, n-1) * sign;
+                sign = -sign;
+            }
+        }
+        return det;
+    }
+    //Driver Method
+    public static void main(String [] args){
+        Scanner in = new Scanner(System.in);
+        //Input Matrix
+        System.out.println("Enter matrix size (Square matrix only)");
+        int n = in.nextInt();
+        System.out.println("Enter matrix");
+        int a [][] = new int [n][n];
+        for(int i=0;i<n;i++){
+            for(int j=0;j<n;j++){
+                a[i][j] = in.nextInt();
+            }
+        }
+        System.out.println(determinant(a, n));
+    }
+}

From c662f13a84b6e3fdec06c6f698e60df16225b6c4 Mon Sep 17 00:00:00 2001
From: Ojasva Jain <44553464+ojasva@users.noreply.github.com>
Date: Tue, 5 Oct 2021 01:20:18 +0530
Subject: [PATCH 3/8] Delete HillCipher.java

---
 Ciphers/HillCipher.java | 172 ----------------------------------------
 1 file changed, 172 deletions(-)
 delete mode 100644 Ciphers/HillCipher.java

diff --git a/Ciphers/HillCipher.java b/Ciphers/HillCipher.java
deleted file mode 100644
index 0a3b50308d21..000000000000
--- a/Ciphers/HillCipher.java
+++ /dev/null
@@ -1,172 +0,0 @@
-package Ciphers;
-
-import java.util.*;
-
-/*
-* Java Implementation of Hill Cipher
-* Hill cipher is a polyalphabetic substitution cipher. Each letter is represented by a number belonging to the set Z26 where A=0 , B=1, ..... Z=25.
-* To encrypt a message, each block of n letters (since matrix size is n x n) is multiplied by an invertible n × n matrix, against modulus 26.
-* To decrypt the message, each block is multiplied by the inverse of the matrix used for encryption.
-* The cipher key and plaintext/ciphertext are user inputs.
-* @author Ojasva Jain
-*/
-
-public class HillCipher{
-static Scanner in = new Scanner (System.in);
-
-/* Following function encrypts the message
-*/
-static void encrypt(String message)
-{
-    message = message.toUpperCase();
-    // Get key matrix
-    System.out.println("Enter key matrix size");
-    int n = in.nextInt();
-    System.out.println("Enter Key/encryptionKey matrix ");
-    int keyMatrix[][] = new int [n][n];
-    for(int i=0;i<n;i++){
-        for(int j=0;j<n;j++){
-            keyMatrix[i][j] = in.nextInt();
-        }
-    }
-    //check if det = 0
-    if(determinant(keyMatrix,n)%26 == 0)
-    {
-        System.out.println("Invalid key, as determinant = 0. Program Terminated");
-        return;
-    }
-
-    int [][]messageVector = new int[n][1];
-    String CipherText="";
-    int cipherMatrix [][] = new int [n][1];
-    int j = 0;
-    while(j<message.length()){
-    for (int i = 0; i < n; i++){
-        if(j>=message.length()){ messageVector[i][0] = 23;}
-        else
-        messageVector[i][0] = (message.charAt(j))%65;
-        System.out.println(messageVector[i][0]);
-        j++; 
-    }
-    int x, i;
-    for (i = 0; i < n; i++)
-    {
-        cipherMatrix[i][0] = 0;
-
-            for (x = 0; x < n; x++)
-            {
-                cipherMatrix[i][0] += keyMatrix[i][x] * messageVector[x][0];
-            }
-            System.out.println(cipherMatrix[i][0]);
-            cipherMatrix[i][0] = cipherMatrix[i][0] % 26;
-        }
-    for (i = 0; i < n; i++)
-    CipherText += (char)(cipherMatrix[i][0] + 65);
-}
-System.out.println("Ciphertext: "+ CipherText);
-}
-//Following function decrypts a message
-static void decrypt(String message)
-{
-    message = message.toUpperCase();
-    // Get key matrix
-    System.out.println("Enter key matrix size");
-    int n = in.nextInt();
-    System.out.println("Enter inverseKey/decryptionKey matrix ");
-    int keyMatrix[][] = new int [n][n];
-    for(int i=0;i<n;i++){
-        for(int j=0;j<n;j++){
-            keyMatrix[i][j] = in.nextInt();
-        }
-    }
-    //check if det = 0
-    if(determinant(keyMatrix,n)%26 == 0)
-    {
-        System.out.println("Invalid key, as determinant = 0. Program Terminated");
-        return;
-    }
-    //solving for the required plaintext message
-    int [][]messageVector = new int[n][1];
-    String PlainText="";
-    int plainMatrix [][] = new int [n][1];
-    int j = 0;
-    while(j<message.length()){
-        for (int i = 0; i < n; i++){
-            if(j>=message.length()){ messageVector[i][0] = 23;}
-            else
-            messageVector[i][0] = (message.charAt(j))%65;
-            System.out.println(messageVector[i][0]);
-            j++; 
-        }
-        int x, i;
-        for (i = 0; i < n; i++)
-        {
-            plainMatrix[i][0] = 0;
-    
-                for (x = 0; x < n; x++)
-                {
-                    plainMatrix[i][0] += keyMatrix[i][x] * messageVector[x][0];
-                }
-    
-                plainMatrix[i][0] = plainMatrix[i][0] % 26;
-            }
-        for (i = 0; i < n; i++)
-        PlainText += (char)(plainMatrix[i][0] + 65);
-    }
-    System.out.println("Plaintext: "+PlainText);
-}
-
-// Determinant calculator
-public static int determinant(int a[][], int n){
-    int det = 0, sign = 1, p = 0, q = 0;
-
-    if(n==1){
-        det = a[0][0];
-    }
-    else{
-        int b[][] = new int[n-1][n-1];
-        for(int x = 0 ; x < n ; x++){
-            p=0;q=0;
-            for(int i = 1;i < n; i++){
-                for(int j = 0; j < n;j++){
-                    if(j != x){
-                        b[p][q++] = a[i][j];
-                        if(q % (n-1) == 0){
-                            p++;
-                            q=0;
-                        }
-                    }
-                }
-            }
-            det = det + a[0][x] *determinant(b, n-1) * sign;
-            sign = -sign;
-        }
-    }
-    return det;
-}
-
-// Function to implement Hill Cipher
-static void hillcipher(String message)
-{
-    message.toUpperCase();
-    System.out.println("What do you want to process from the message?");
-    System.out.println("Press 1: To Encrypt");
-    System.out.println("Press 2: To Decrypt");
-    short sc = in.nextShort();
-    if(sc == 1)
-    encrypt(message);
-    else if(sc == 2)
-    decrypt(message);
-    else
-    System.out.println("Invalid input, program terminated.");
-}
-
-// Driver code
-public static void main(String[] args)
-   {
-    // Get the message to be encrypted
-    System.out.println("Enter message");
-    String message = in.nextLine();
-    hillcipher(message);
-    }
-}

From 457036712be2f8b4fe3767ef260e0ee68264bb6d Mon Sep 17 00:00:00 2001
From: Ojasva Jain <44553464+ojasva@users.noreply.github.com>
Date: Tue, 5 Oct 2021 01:22:36 +0530
Subject: [PATCH 4/8] Add files via upload

---
 Ciphers/HillCipher.java | 172 ++++++++++++++++++++++++++++++++++++++++
 1 file changed, 172 insertions(+)
 create mode 100644 Ciphers/HillCipher.java

diff --git a/Ciphers/HillCipher.java b/Ciphers/HillCipher.java
new file mode 100644
index 000000000000..0a3b50308d21
--- /dev/null
+++ b/Ciphers/HillCipher.java
@@ -0,0 +1,172 @@
+package Ciphers;
+
+import java.util.*;
+
+/*
+* Java Implementation of Hill Cipher
+* Hill cipher is a polyalphabetic substitution cipher. Each letter is represented by a number belonging to the set Z26 where A=0 , B=1, ..... Z=25.
+* To encrypt a message, each block of n letters (since matrix size is n x n) is multiplied by an invertible n × n matrix, against modulus 26.
+* To decrypt the message, each block is multiplied by the inverse of the matrix used for encryption.
+* The cipher key and plaintext/ciphertext are user inputs.
+* @author Ojasva Jain
+*/
+
+public class HillCipher{
+static Scanner in = new Scanner (System.in);
+
+/* Following function encrypts the message
+*/
+static void encrypt(String message)
+{
+    message = message.toUpperCase();
+    // Get key matrix
+    System.out.println("Enter key matrix size");
+    int n = in.nextInt();
+    System.out.println("Enter Key/encryptionKey matrix ");
+    int keyMatrix[][] = new int [n][n];
+    for(int i=0;i<n;i++){
+        for(int j=0;j<n;j++){
+            keyMatrix[i][j] = in.nextInt();
+        }
+    }
+    //check if det = 0
+    if(determinant(keyMatrix,n)%26 == 0)
+    {
+        System.out.println("Invalid key, as determinant = 0. Program Terminated");
+        return;
+    }
+
+    int [][]messageVector = new int[n][1];
+    String CipherText="";
+    int cipherMatrix [][] = new int [n][1];
+    int j = 0;
+    while(j<message.length()){
+    for (int i = 0; i < n; i++){
+        if(j>=message.length()){ messageVector[i][0] = 23;}
+        else
+        messageVector[i][0] = (message.charAt(j))%65;
+        System.out.println(messageVector[i][0]);
+        j++; 
+    }
+    int x, i;
+    for (i = 0; i < n; i++)
+    {
+        cipherMatrix[i][0] = 0;
+
+            for (x = 0; x < n; x++)
+            {
+                cipherMatrix[i][0] += keyMatrix[i][x] * messageVector[x][0];
+            }
+            System.out.println(cipherMatrix[i][0]);
+            cipherMatrix[i][0] = cipherMatrix[i][0] % 26;
+        }
+    for (i = 0; i < n; i++)
+    CipherText += (char)(cipherMatrix[i][0] + 65);
+}
+System.out.println("Ciphertext: "+ CipherText);
+}
+//Following function decrypts a message
+static void decrypt(String message)
+{
+    message = message.toUpperCase();
+    // Get key matrix
+    System.out.println("Enter key matrix size");
+    int n = in.nextInt();
+    System.out.println("Enter inverseKey/decryptionKey matrix ");
+    int keyMatrix[][] = new int [n][n];
+    for(int i=0;i<n;i++){
+        for(int j=0;j<n;j++){
+            keyMatrix[i][j] = in.nextInt();
+        }
+    }
+    //check if det = 0
+    if(determinant(keyMatrix,n)%26 == 0)
+    {
+        System.out.println("Invalid key, as determinant = 0. Program Terminated");
+        return;
+    }
+    //solving for the required plaintext message
+    int [][]messageVector = new int[n][1];
+    String PlainText="";
+    int plainMatrix [][] = new int [n][1];
+    int j = 0;
+    while(j<message.length()){
+        for (int i = 0; i < n; i++){
+            if(j>=message.length()){ messageVector[i][0] = 23;}
+            else
+            messageVector[i][0] = (message.charAt(j))%65;
+            System.out.println(messageVector[i][0]);
+            j++; 
+        }
+        int x, i;
+        for (i = 0; i < n; i++)
+        {
+            plainMatrix[i][0] = 0;
+    
+                for (x = 0; x < n; x++)
+                {
+                    plainMatrix[i][0] += keyMatrix[i][x] * messageVector[x][0];
+                }
+    
+                plainMatrix[i][0] = plainMatrix[i][0] % 26;
+            }
+        for (i = 0; i < n; i++)
+        PlainText += (char)(plainMatrix[i][0] + 65);
+    }
+    System.out.println("Plaintext: "+PlainText);
+}
+
+// Determinant calculator
+public static int determinant(int a[][], int n){
+    int det = 0, sign = 1, p = 0, q = 0;
+
+    if(n==1){
+        det = a[0][0];
+    }
+    else{
+        int b[][] = new int[n-1][n-1];
+        for(int x = 0 ; x < n ; x++){
+            p=0;q=0;
+            for(int i = 1;i < n; i++){
+                for(int j = 0; j < n;j++){
+                    if(j != x){
+                        b[p][q++] = a[i][j];
+                        if(q % (n-1) == 0){
+                            p++;
+                            q=0;
+                        }
+                    }
+                }
+            }
+            det = det + a[0][x] *determinant(b, n-1) * sign;
+            sign = -sign;
+        }
+    }
+    return det;
+}
+
+// Function to implement Hill Cipher
+static void hillcipher(String message)
+{
+    message.toUpperCase();
+    System.out.println("What do you want to process from the message?");
+    System.out.println("Press 1: To Encrypt");
+    System.out.println("Press 2: To Decrypt");
+    short sc = in.nextShort();
+    if(sc == 1)
+    encrypt(message);
+    else if(sc == 2)
+    decrypt(message);
+    else
+    System.out.println("Invalid input, program terminated.");
+}
+
+// Driver code
+public static void main(String[] args)
+   {
+    // Get the message to be encrypted
+    System.out.println("Enter message");
+    String message = in.nextLine();
+    hillcipher(message);
+    }
+}

From 2821b9f610d0ff191bab16d831ed2a5e023ba855 Mon Sep 17 00:00:00 2001
From: Ojasva Jain <44553464+ojasva@users.noreply.github.com>
Date: Tue, 5 Oct 2021 01:31:17 +0530
Subject: [PATCH 5/8] Delete DeterminantOfMatrix.java

---
 Maths/DeterminantOfMatrix.java | 61 ----------------------------------
 1 file changed, 61 deletions(-)
 delete mode 100644 Maths/DeterminantOfMatrix.java

diff --git a/Maths/DeterminantOfMatrix.java b/Maths/DeterminantOfMatrix.java
deleted file mode 100644
index f5ed09ca167d..000000000000
--- a/Maths/DeterminantOfMatrix.java
+++ /dev/null
@@ -1,61 +0,0 @@
-package Maths;
-import java.util.*;
-
-/* 
-* @author Ojasva Jain
-* Determinant of Matrix Wikipedia link : https://en.wikipedia.org/wiki/Determinant
-*/
-public class DeterminantOfMatrix
-{
-    // Determinant calculator
-    //@return determinant of the input matrix
-    static int determinant(int a[][], int n)
-    {
-        int det = 0, sign = 1, p = 0, q = 0;
-        if(n==1)
-        {
-            det = a[0][0];
-        }
-        else
-        {
-            int b[][] = new int[n-1][n-1];
-            for(int x = 0 ; x < n ; x++)
-            {
-                p=0;q=0;
-                for(int i = 1;i < n; i++)
-                {
-                    for(int j = 0; j < n;j++)
-                    {
-                        if(j != x)
-                        {
-                            b[p][q++] = a[i][j];
-                            if(q % (n-1) == 0)
-                            {
-                                p++;
-                                q=0;
-                            }
-                        }
-                    }
-                }
-                det = det + a[0][x] *determinant(b, n-1) * sign;
-                sign = -sign;
-            }
-        }
-        return det;
-    }
-    //Driver Method
-    public static void main(String [] args){
-        Scanner in = new Scanner(System.in);
-        //Input Matrix
-        System.out.println("Enter matrix size (Square matrix only)");
-        int n = in.nextInt();
-        System.out.println("Enter matrix");
-        int a [][] = new int [n][n];
-        for(int i=0;i<n;i++){
-            for(int j=0;j<n;j++){
-                a[i][j] = in.nextInt();
-            }
-        }
-        System.out.println(determinant(a, n));
-    }
-}

From d952e38c742d45fdf150709d56b8e5619de8b931 Mon Sep 17 00:00:00 2001
From: Ojasva Jain <44553464+ojasva@users.noreply.github.com>
Date: Wed, 6 Oct 2021 15:23:14 +0530
Subject: [PATCH 6/8] DeterminantOfMatrix

Finding determinant of a matrix.
---
 Maths/DeterminantOfMatrix.java | 61 ++++++++++++++++++++++++++++++++++
 1 file changed, 61 insertions(+)
 create mode 100644 Maths/DeterminantOfMatrix.java

diff --git a/Maths/DeterminantOfMatrix.java b/Maths/DeterminantOfMatrix.java
new file mode 100644
index 000000000000..f5ed09ca167d
--- /dev/null
+++ b/Maths/DeterminantOfMatrix.java
@@ -0,0 +1,61 @@
+package Maths;
+import java.util.*;
+
+/* 
+* @author Ojasva Jain
+* Determinant of Matrix Wikipedia link : https://en.wikipedia.org/wiki/Determinant
+*/
+public class DeterminantOfMatrix
+{
+    // Determinant calculator
+    //@return determinant of the input matrix
+    static int determinant(int a[][], int n)
+    {
+        int det = 0, sign = 1, p = 0, q = 0;
+        if(n==1)
+        {
+            det = a[0][0];
+        }
+        else
+        {
+            int b[][] = new int[n-1][n-1];
+            for(int x = 0 ; x < n ; x++)
+            {
+                p=0;q=0;
+                for(int i = 1;i < n; i++)
+                {
+                    for(int j = 0; j < n;j++)
+                    {
+                        if(j != x)
+                        {
+                            b[p][q++] = a[i][j];
+                            if(q % (n-1) == 0)
+                            {
+                                p++;
+                                q=0;
+                            }
+                        }
+                    }
+                }
+                det = det + a[0][x] *determinant(b, n-1) * sign;
+                sign = -sign;
+            }
+        }
+        return det;
+    }
+    //Driver Method
+    public static void main(String [] args){
+        Scanner in = new Scanner(System.in);
+        //Input Matrix
+        System.out.println("Enter matrix size (Square matrix only)");
+        int n = in.nextInt();
+        System.out.println("Enter matrix");
+        int a [][] = new int [n][n];
+        for(int i=0;i<n;i++){
+            for(int j=0;j<n;j++){
+                a[i][j] = in.nextInt();
+            }
+        }
+        System.out.println(determinant(a, n));
+    }
+}

From 2e219d026b2a4d848a49081531e3e1b49bb20e2a Mon Sep 17 00:00:00 2001
From: Ojasva Jain <44553464+ojasva@users.noreply.github.com>
Date: Tue, 12 Oct 2021 17:03:09 +0530
Subject: [PATCH 7/8] Inverse Of a Square Matrix

This feature finds inverse of a matrix using gaussian elimination.
---
 Misc/InverseOfMatrix.java | 130 ++++++++++++++++++++++++++++++++++++++
 1 file changed, 130 insertions(+)
 create mode 100644 Misc/InverseOfMatrix.java

diff --git a/Misc/InverseOfMatrix.java b/Misc/InverseOfMatrix.java
new file mode 100644
index 000000000000..f229e8c86088
--- /dev/null
+++ b/Misc/InverseOfMatrix.java
@@ -0,0 +1,130 @@
+import java.util.Scanner;
+ 
+/*
+* Wikipedia link : https://en.wikipedia.org/wiki/Invertible_matrix
+*
+* Here we use gauss elimination method to find the inverse of a given matrix.
+* To understand gauss elimination method to find inverse of a matrix: https://www.sangakoo.com/en/unit/inverse-matrix-method-of-gaussian-elimination
+*
+* We can also find the inverse of a matrix 
+*/
+public class InverseOfMatrix 
+{
+    public static void main(String argv[]) 
+    {
+        Scanner input = new Scanner(System.in);
+        System.out.println("Enter the matrix size (Square matrix only): ");
+        int n = input.nextInt();
+        double a[][]= new double[n][n];
+        System.out.println("Enter the elements of matrix: ");
+        for(int i=0; i<n; i++)
+            for(int j=0; j<n; j++)
+                a[i][j] = input.nextDouble();
+ 
+        double d[][] = invert(a);
+        System.out.println();
+        System.out.println("The inverse is: ");
+        for (int i=0; i<n; ++i) 
+        {
+            for (int j=0; j<n; ++j)
+            {
+                System.out.print(d[i][j]+"  ");
+            }
+            System.out.println();
+        }
+        input.close();
+    }	
+ 
+    public static double[][] invert(double a[][]) 
+    {
+        int n = a.length;
+        double x[][] = new double[n][n];
+        double b[][] = new double[n][n];
+        int index[] = new int[n];
+        for (int i=0; i<n; ++i) 
+            b[i][i] = 1;
+ 
+ // Transform the matrix into an upper triangle
+        gaussian(a, index);
+ 
+ // Update the matrix b[i][j] with the ratios stored
+        for (int i=0; i<n-1; ++i)
+            for (int j=i+1; j<n; ++j)
+                for (int k=0; k<n; ++k)
+                    b[index[j]][k]
+                    	    -= a[index[j]][i]*b[index[i]][k];
+ 
+ // Perform backward substitutions
+        for (int i=0; i<n; ++i) 
+        {
+            x[n-1][i] = b[index[n-1]][i]/a[index[n-1]][n-1];
+            for (int j=n-2; j>=0; --j) 
+            {
+                x[j][i] = b[index[j]][i];
+                for (int k=j+1; k<n; ++k) 
+                {
+                    x[j][i] -= a[index[j]][k]*x[k][i];
+                }
+                x[j][i] /= a[index[j]][j];
+            }
+        }
+        return x;
+    }
+ 
+// Method to carry out the partial-pivoting Gaussian
+// elimination.  Here index[] stores pivoting order.
+ 
+    public static void gaussian(double a[][], int index[]) 
+    {
+        int n = index.length;
+        double c[] = new double[n];
+ 
+ // Initialize the index
+        for (int i=0; i<n; ++i) 
+            index[i] = i;
+ 
+ // Find the rescaling factors, one from each row
+        for (int i=0; i<n; ++i) 
+        {
+            double c1 = 0;
+            for (int j=0; j<n; ++j) 
+            {
+                double c0 = Math.abs(a[i][j]);
+                if (c0 > c1) c1 = c0;
+            }
+            c[i] = c1;
+        }
+ 
+ // Search the pivoting element from each column
+        int k = 0;
+        for (int j=0; j<n-1; ++j) 
+        {
+            double pi1 = 0;
+            for (int i=j; i<n; ++i) 
+            {
+                double pi0 = Math.abs(a[index[i]][j]);
+                pi0 /= c[index[i]];
+                if (pi0 > pi1) 
+                {
+                    pi1 = pi0;
+                    k = i;
+                }
+            }
+   // Interchange rows according to the pivoting order
+            int itmp = index[j];
+            index[j] = index[k];
+            index[k] = itmp;
+            for (int i=j+1; i<n; ++i) 	
+            {
+                double pj = a[index[i]][j]/a[index[j]][j];
+ 
+ // Record pivoting ratios below the diagonal
+                a[index[i]][j] = pj;
+ 
+ // Modify other elements accordingly
+                for (int l=j+1; l<n; ++l)
+                    a[index[i]][l] -= pj*a[index[j]][l];
+            }
+        }
+    }
+}
\ No newline at end of file

From e7c888a5c720c795a29e9f47f93b8340ebcb2c9a Mon Sep 17 00:00:00 2001
From: Ojasva Jain <44553464+ojasva@users.noreply.github.com>
Date: Sat, 16 Oct 2021 18:50:31 +0530
Subject: [PATCH 8/8] Update InverseOfMatrix.java

---
 Misc/InverseOfMatrix.java | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/Misc/InverseOfMatrix.java b/Misc/InverseOfMatrix.java
index f229e8c86088..ed11d77ed205 100644
--- a/Misc/InverseOfMatrix.java
+++ b/Misc/InverseOfMatrix.java
@@ -1,3 +1,4 @@
+package Misc;
 import java.util.Scanner;
  
 /*
@@ -127,4 +128,4 @@ public static void gaussian(double a[][], int index[])
             }
         }
     }
-}
\ No newline at end of file
+}