1329. Sort the Matrix Diagonally

 1329. Sort the Matrix Diagonally

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

	class Solution {
	public:
	vector<vector<int>> diagonalSort(vector<vector<int>>& mat) {
	vector<int> d;
	int m = mat.size();
	int n = mat[0].size();
	// Save each diagonal to Hash
	unordered_map<int, priority_queue<int, vector<int>, greater<>>> hash;
	for(int i = 0; i < m; i++){
	for(int j = 0; j < n; j++){
	// diff of row & col is same key
	int key = i - j;
	hash[key].push(mat[i][j]);
	}
	}
	// generate ans
	for(int i = 0; i < m; i++){
	for(int j = 0; j < n; j++){
	int key = i - j;
	mat[i][j] = hash[key].top();
	hash[key].pop();
	}
	}
	return mat;
	}
	};

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