2352. Equal Row and Column Pairs

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2352. Equal Row and Column Pairs

Description

Given a 0-indexed n x n integer matrix grid, return the number of pairs (r<sub>i</sub>, c<sub>j</sub>) such that row r<sub>i</sub> and column c<sub>j</sub> 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:

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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:

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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] <= 10^5

Hints/Notes

Solution

Language: C++

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class Solution {
public:
    int equalPairs(vector<vector<int>>& grid) {
        unordered_map<string, int> rows;
        int n = grid.size();
        for (int i = 0; i < n; i++) {
            string cur;
            for (int j = 0; j < n; j++) {
                cur += to_string(grid[i][j]) + ',';
            }
            rows[cur]++;
        }
        int res = 0;
        for (int j = 0; j < n; j++) {
            string cur;
            for (int i = 0; i < n; i++) {
                cur += to_string(grid[i][j]) + ',';
            }
            res += rows[cur];
        }
        return res;
    }
};