Add Determinant Of a Matrix [Hacktoberfest] (TheAlgorithms#2508)

ojasva · web-flow · commit 5b8bcf0c63fb · 2021-10-11T13:51:26.000+03:00
diff --git a/Maths/DeterminantOfMatrix.java 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));
+    }
+}
