Question

1329. Sort the Matrix Diagonally

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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

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

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;
  }
}

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;
  }
};

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
}