const diagonalSum = function (arr) {
    var length=arr.length -1;
     var sum=0;
     for(let i=0;i<arr.length;i  ){//1<3
         sum = arr[i][i] arr[i][length-i]//[1][0] 
     }
       return sum;
   };

tried this , but 2nd and 3rd test cases are not getting passed. Any other logic?

const diagonalSum = function (arr) {
    var length=arr.length -1;
     var sum=0;
     for(let i=0;i<arr.length;i  ){//1<3
         sum = arr[i][i] arr[i][length-i]//[1][0] 
     }
       return sum;
   };

searching any other logic

CodePudding user response：

If you are trying to find the diagonal sum of both the diagonals of 2d Array using single for loop, below is the solution

const diagonalSum = function (arr) {
  sum = 0;
  for (let i = 0; i < arr.length; i  ) {
    sum = sum   arr[i][i]   arr[i][(arr[i].length - 1) - i]
  }
  return sum;
};

CodePudding user response：

Your code looks good to me. Here are a few test cases:

const diagonalSum = function (arr) {
  let maxIdx = arr.length - 1;
  let sum = 0;
  for(let i=0; i < arr.length; i  ) {
    sum  = arr[i][i]   arr[i][maxIdx-i];
  }
  return sum;
};

const matrix1 = [
  [1, 1, 1],
  [1, 1, 1],
  [1, 1, 1]
];
const matrix2 = [
  [1, 2, 3],
  [4, 5, 6],
  [7, 8, 0]
];
const matrix3 = [
  [1, 1, 1, 1],
  [1, 1, 1, 1],
  [1, 1, 1, 1],
  [1, 1, 1, 1]
];
console.log({
  matrix1: diagonalSum(matrix1),
  matrix2: diagonalSum(matrix2),
  matrix3: diagonalSum(matrix3)
});

Output:

{
  "matrix1": 6,
  "matrix2": 21,
  "matrix3": 8
}

Please provide a some test cases that fail.

CodePudding user response：

This will work for you.

// An efficient Javascript program to find // sum of diagonals

function  printDiagonalSums(mat,n)
    {
        let principal = 0, secondary = 0;
        for (let i = 0; i < n; i  ) {
            principal  = mat[i][i];
            
        }
     
        document.write("Principal Diagonal:"
                                  principal "<br>");
                                     
        
    }
     
    // Driver code
     
        let a = [[ 1, 2, 3, 4, 5],
                    [5, 6, 7, 8, 5 ],
                    [ 1, 2, 3, 4, 5 ],
                    [ 5, 6, 7, 8, 5],
                [ 5, 6, 7, 8, 5]];
     
        printDiagonalSums(a, 5);