LeetCode75——Day23

叶卡捷琳堡2023-11-02 9:17

文章目录

- 一、题目
- 二、题解

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

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

cpp 复制代码

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;
    }
};