LeetCode 2352. 相等行列对

输入：grid = [[3,2,1],[1,7,6],[2,7,7]]
输出：1
解释：存在一对相等行列对：
- (第 2 行，第 1 列)：[2,7,7]

输入：grid = [[3,1,2,2],[1,4,4,5],[2,4,2,2],[2,4,2,2]]
输出：3
解释：存在三对相等行列对：
- (第 0 行，第 0 列)：[3,1,2,2]
- (第 2 行, 第 2 列)：[2,4,2,2]
- (第 3 行, 第 2 列)：[2,4,2,2]
 
提示：
n == grid.length == grid[i].length
1 <= n <= 200
1 <= grid[i][j] <= 10^5

class Solution:
    def equalPairs(self, grid: List[List[int]]) -> int:
        n = len(grid)
        m = defaultdict(list) # v: [idx ]
        for i in range(n):
            m[grid[0][i]].append(i)
        def same(x, y):
            for i in range(n):
                if grid[x][i] != grid[i][y]:
                    return False
            return True
        ans = 0
        for i in range(n):
            for j in m[grid[i][0]]:
                if same(i, j):
                    ans += 1
        return ans

class Solution:
    def equalPairs(self, grid: List[List[int]]) -> int:
        n = len(grid)
        g2 = [[0 for i in range(n)] for j in range(n)]
        for i in range(n):
            for j in range(n):
                g2[i][j] = grid[j][i]
        ans = 0
        for i in range(n):
            for j in range(n):
                if g2[i] == grid[j]:
                    ans += 1
        return ans