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

解題

先建立 map 來儲存 相異 row 出現的次數，再與 column 進行比較和答案的加總。

func equalPairs(grid [][]int) int {
    m := make(map[string]int)
    res := 0

    for i:=0; i<len(grid); i++ {
        s := ""
        for j:=0; j<len(grid[0]); j++ {
            s += strconv.Itoa(grid[i][j])
            s += "/"
        }

        m[s]++
    }

    for i:=0; i<len(grid[0]); i++ {
        s := ""
        for j:=0; j<len(grid); j++ {
            s += strconv.Itoa(grid[j][i])
            s += "/"
        }

        if m[s]!=0 {
            res += m[s]
        } 
    }

    return res
}