1329. Sort the Matrix Diagonally (M)

Sort the Matrix Diagonally (M)

题目

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]]

Constraints:

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

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题意

将一个矩阵的元素按照对角线进行排序。

思路

直接将每个对角线拉出来放入一个数组，排序后再放回即可。

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代码实现

Java

class Solution {
    public int[][] diagonalSort(int[][] mat) {
        int m = mat.length, n = mat[0].length;
        for (int i = 0; i < m; i++) {
            sort(mat, i, 0);
        }
        for (int i = 1; i < n; i++) {
            sort(mat, 0, i);
        }
        return mat;
    }

    private void sort(int[][] mat, int i, int j) {
        int m = mat.length, n = mat[0].length;
        int size = Math.min(m - i, n - j);
        int[] tmp = new int[size];
        for (int k = 0; k < size; k++) {
            tmp[k] = mat[i + k][j + k];
        }
        Arrays.sort(tmp);
        for (int k = 0; k < size; k++) {
            mat[i + k][j + k] = tmp[k];
        }
    }
}