package ArrayBasedProblems;

public class DiagonalSum {

public static void main(String[] args) {

int[][] matrix = { { 1, 2, 3 }, { 4, 5, 6 }, { 7, 8, 9 } };

System.out.println("Diagonal sum: " + diagonalSum(matrix));

}

public static int diagonalSum(int[][] matrix) { // O(n) time and O(1) space

int sum = 0;

for (int i = 0; i < matrix.length; i++) {

sum += matrix[i][i];

if (i != matrix.length - i - 1) {

sum += matrix[i][matrix.length - i - 1];

}

}

return sum;

}

public int bruceForce(int[][] mat) { // O(n^2) time and O(1) space

int sum = 0;

int col = mat[0].length-1;

for(int i =0;i<mat.length;i++) {

for(int j = 0;j<mat[0].length;j++) {

if(i==j || j==(col-i)){

System.out.println(mat[i][j]);

sum += mat[i][j];

}

}

}

return sum;

}

}