Leetcode-1572 Matrix Diagonal Sum Solution in Java | Hindi Coding Community

 Given a square matrix mat, having size nxn you have to return the sum of the matrix diagonals.

You have to only include the sum of all the elements on the primary diagonal and all the elements on the secondary diagonal that are not part of the primary diagonal. Find out the sum of them.

 

Example 1:

Input: mat = [[1,2,3],
              [4,5,6],
              [7,8,9]]
Output: 25
Explanation: Diagonals sum: 1 + 5 + 9 + 3 + 7 = 25
Notice that element mat[1][1] = 5 is counted only once.

Example 2:

Input: mat = [[1,1,1,1],
              [1,1,1,1],
              [1,1,1,1],
              [1,1,1,1]]
Output: 8

Example 3:

Input: mat = [[5]]
Output: 5

 

Constraints:

• n == mat.length == mat[i].length
• 1 <= n <= 100
• 1 <= mat[i][j] <= 100

Java Code :

class Solution {

public int diagonalSum(int[][] mat) {

if(mat.length==1)

return mat[0][0];

if(mat.length==2)

return mat[0][0]+mat[0][1]+mat[1][0]+mat[1][1];

int length=mat.length-2;

int[][] m= new int[length][length];

for(int i=0;i<length;i++)

{

for(int j=0;j<length;j++)

{

m[i][j]=mat[i+1][j+1];

}

}

return mat[0][0]+mat[0][length+1]+mat[length+1][0]+mat[length+1][length+1] +diagonalSum(m);

}

}