Qn - Equal Row and Column Pairs

Equal Row and Column Pairs

Question

Given a 0-indexed n x n integer matrix grid, return the number of pairs (r<sub>i</sub>, c<sub>j</sub>) such that row r<sub>i</sub> and column c<sub>j</sub> 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] <= 10^5

Hints

Hint 1

We can use nested loops to compare every row against every column.

Hint 2

Another loop is necessary to compare the row and column element by element.

Hint 3

It is also possible to hash the arrays and compare the hashed values instead.