LeetCode 1329: Sort the Matrix Diagonally Solution

Master LeetCode problem 1329 (Sort the Matrix Diagonally), a medium challenge, with our optimized solutions in Java, C++, and Python. Explore detailed explanations, test your code in our interactive editor, and prepare for coding interviews.

1329. Sort the Matrix Diagonally

Medium

Array Sorting Matrix

Problem Explanation

Explanation

To sort each diagonal in the matrix, we can iterate through each diagonal and sort the elements in it. We can use a hashmap to store elements of each diagonal based on their diagonal index. After storing all elements, we can sort the elements in each diagonal and put them back in the matrix.

Initialize a hashmap to store elements based on their diagonal index.
Iterate through each element in the matrix and store it in the hashmap based on its diagonal index.
Sort the elements in each diagonal.
Put the sorted elements back in the matrix.

Time complexity: O(mnlog(min(m,n)))
Space complexity: O(m*n)

Solution Code

class Solution {
    public int[][] diagonalSort(int[][] mat) {
        int m = mat.length;
        int n = mat[0].length;
        
        Map<Integer, PriorityQueue<Integer>> map = new HashMap<>();
        
        for (int i = 0; i < m; i++) {
            for (int j = 0; j < n; j++) {
                int diagonalIndex = i - j;
                map.putIfAbsent(diagonalIndex, new PriorityQueue<>());
                map.get(diagonalIndex).add(mat[i][j]);
            }
        }
        
        for (int i = 0; i < m; i++) {
            for (int j = 0; j < n; j++) {
                int diagonalIndex = i - j;
                mat[i][j] = map.get(diagonalIndex).poll();
            }
        }
        
        return mat;
    }
}

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