Equal Row and Column Pairs LeetCode Solution

Problem – Equal Row and Column Pairs LeetCode Solution

Given a 0-indexed n x n integer matrix gridreturn 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

Equal Row and Column Pairs LeetCode Solution in C++

class Solution {
public:
    int equalPairs(vector<vector<int>>& grid) 
    {
        // Number to store the count of equal pairs.
        int ans = 0;
        map<vector<int>, int> mp;
        // Storing each row int he map
        for (int i = 0; i < grid.size(); i++)
            mp[grid[i]]++;
        
        for (int i = 0; i < grid[0].size(); i++)
        {
            vector<int> v;
            // extracting column in a vector.
            for (int j = 0; j < grid.size(); j++)
                v.push_back(grid[j][i]);
            // Add the number of times that column appeared as a row.
            ans += mp[v];
        }
        // Return the number of count
        return ans;
    }
};

Equal Row and Column Pairs LeetCode Solution in Java

public int equalPairs(int[][] grid) {
    int res = 0, n = grid.length;
    HashMap<String, Integer> x = new HashMap<>();
	HashMap<String, Integer> y = new HashMap<>();
	
    for(int i=0; i<n; i++){
        StringBuilder sb1 = new StringBuilder(), sb2 = new StringBuilder();
        for(int j=0; j<n; j++){
            sb1.append(grid[i][j]);
            sb2.append(grid[j][i]);
            sb1.append(','); sb2.append(',');
        }
        String curr1 = sb1.toString(), curr2 = sb2.toString();
        x.put(curr1, x.getOrDefault(curr1, 0)+1);
        y.put(curr2, y.getOrDefault(curr2, 0)+1);
    }
    
    for(String str : x.keySet())
        if(y.containsKey(str))
            res += x.get(str)*y.get(str);
    return res;
}

Equal Row and Column Pairs LeetCode Solution in Python

    def equalPairs(self, A):
        count = Counter(zip(*A))
        return sum(count[tuple(r)] for r in A)
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