2352

2352. Equal Row and Column Pairs (Medium)

Given a 0-indexed n x n integer matrix grid, return the number of pairs (ri, cj) such that row ri and column cj are equal.

A row and column pair is considered equal if they contain the same elements in the same order (i.e., an equal array).

 

Example 1:

Input: grid = [[3,2,1],[1,7,6],[2,7,7]]
Output: 1
Explanation: There is 1 equal row and column pair:
- (Row 2, Column 1): [2,7,7]

Example 2:

Input: grid = [[3,1,2,2],[1,4,4,5],[2,4,2,2],[2,4,2,2]]
Output: 3
Explanation: There are 3 equal row and column pairs:
- (Row 0, Column 0): [3,1,2,2]
- (Row 2, Column 2): [2,4,2,2]
- (Row 3, Column 2): [2,4,2,2]

 

Constraints:

• n == grid.length == grid[i].length
• 1 <= n <= 200
• 1 <= grid[i][j] <= 105

Companies: Adobe, Apple, Amazon

Related Topics:
Array, Hash Table, Matrix, Simulation

Similar Questions:

• Delete Greatest Value in Each Row (Easy)

Solution 1.

// OJ: https://leetcode.com/problems/equal-row-and-column-pairs
// Author: github.com/lzl124631x
// Time: O(N^3)
// Space: O(1)
class Solution {
public:
    int equalPairs(vector<vector<int>>& A) {
        int N = A.size(), ans = 0;
        for (int i = 0; i < N; ++i) {
            for (int j = 0; j < N; ++j) {
                bool equal = true;
                for (int k = 0; k < N && equal; ++k) {
                    if (A[i][k] != A[k][j]) equal = false;
                }
                ans += equal;
            }
        }
        return ans;
    }
};