1329. Sort the Matrix Diagonally

Description

A matrix diagonal is a diagonal line of cells starting from some cell in either the topmost row or leftmost column and going in the bottom-right direction until reaching the matrix's end. For example, the matrix diagonal starting from mat[2][0], where mat is a 6 x 3 matrix, includes cells mat[2][0], mat[3][1], and mat[4][2].

Given an m x n matrix mat of integers, sort each matrix diagonal in ascending order and return the resulting matrix.

 

Example 1:

Input: mat = [[3,3,1,1],[2,2,1,2],[1,1,1,2]]
Output: [[1,1,1,1],[1,2,2,2],[1,2,3,3]]

Example 2:

Input: mat = [[11,25,66,1,69,7],[23,55,17,45,15,52],[75,31,36,44,58,8],[22,27,33,25,68,4],[84,28,14,11,5,50]]
Output: [[5,17,4,1,52,7],[11,11,25,45,8,69],[14,23,25,44,58,15],[22,27,31,36,50,66],[84,28,75,33,55,68]]

 

Constraints:

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

Solutions

Solution 1

Python Code
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class Solution:
    def diagonalSort(self, mat: List[List[int]]) -> List[List[int]]:
        m, n = len(mat), len(mat[0])
        for k in range(min(m, n) - 1):
            for i in range(m - 1):
                for j in range(n - 1):
                    if mat[i][j] > mat[i + 1][j + 1]:
                        mat[i][j], mat[i + 1][j + 1] = mat[i + 1][j + 1], mat[i][j]
        return mat

Java Code
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class Solution {
    public int[][] diagonalSort(int[][] mat) {
        int m = mat.length, n = mat[0].length;
        for (int k = 0; k < Math.min(m, n) - 1; ++k) {
            for (int i = 0; i < m - 1; ++i) {
                for (int j = 0; j < n - 1; ++j) {
                    if (mat[i][j] > mat[i + 1][j + 1]) {
                        int t = mat[i][j];
                        mat[i][j] = mat[i + 1][j + 1];
                        mat[i + 1][j + 1] = t;
                    }
                }
            }
        }
        return mat;
    }
}

C++ Code
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class Solution {
public:
    vector<vector<int>> diagonalSort(vector<vector<int>>& mat) {
        int m = mat.size(), n = mat[0].size();
        for (int k = 0; k < min(m, n) - 1; ++k)
            for (int i = 0; i < m - 1; ++i)
                for (int j = 0; j < n - 1; ++j)
                    if (mat[i][j] > mat[i + 1][j + 1])
                        swap(mat[i][j], mat[i + 1][j + 1]);
        return mat;
    }
};

Go Code
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func diagonalSort(mat [][]int) [][]int {
	m, n := len(mat), len(mat[0])
	for k := 0; k < m-1 && k < n-1; k++ {
		for i := 0; i < m-1; i++ {
			for j := 0; j < n-1; j++ {
				if mat[i][j] > mat[i+1][j+1] {
					mat[i][j], mat[i+1][j+1] = mat[i+1][j+1], mat[i][j]
				}
			}
		}
	}
	return mat
}