一、题目
2352. Equal Row and Column Pairs
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文章来源：https://www.toymoban.com/news/detail-738526.html
二、题解
使用map保存键值对（vector<int>作为key，该数组的数目作为值），map底层禹unordered_map不同，基于红黑树文章来源地址https://www.toymoban.com/news/detail-738526.html
class Solution {
public:
int equalPairs(vector<vector<int>>& grid) {
int n = grid.size();
map<vector<int>,int> map;
//添加行
for(int i = 0;i < n;i++){
map[grid[i]]++;
}
int res = 0;
for(int j = 0;j < n;j++){
//添加列
vector<int> arr;
for(int i = 0;i < n;i++){
arr.push_back(grid[i][j]);
}
//如果存在对应的行与其相等，加上对应的行的数目
if(map.find(arr) != map.end()) res += map[arr];
}
return res;
}
};
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