Diagonal Traverse Java Solution - The Coding Shala

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Diagonal Traverse

Problem: 
Given a matrix of M x N elements (M rows, N columns), return all elements of the matrix in diagonal order as shown in the below image.

Example:
Input:
[
 [ 1, 2, 3 ],
 [ 4, 5, 6 ],
 [ 7, 8, 9 ]
]

Output:  [1,2,4,7,5,3,6,8,9]

Explanation:
Diagonal Traverse - The Coding Shala

Diagonal Traverse Java Solution

Approach: 

Traverse the Matrix.

Java Code:: 

class Solution {
    public int[] findDiagonalOrder(int[][] matrix) {
        int row = matrix.length;
        if(row == 0) return (new int[0]); //if empty matrix
        int col = matrix[0].length;
        int[] ans = new int[row*col];
        int index = 0;
        int i =0, j=0;
        
        while(i<row && j<col){
            
            while(i>=0 && j<col){ //moving up
                ans[index] = matrix[i][j];
                index++;
                j++;
                i--;
            }
            i++;
            if(j==col){ //reach beyond column
                i++;
                j--;
            }
            while(j>=0 && i<row){ //moving down
                ans[index] = matrix[i][j];
                index++;
                i++;
                j--;
            }
            j++;
            if(i==row){ //reach beyond row
                i--;
                j++;
            }
           // for(int tmp = 0; tmp<index;tmp++) System.out.print(ans[tmp]+" ");
        }
        return ans;
    }
}



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