2352. Equal Row and Column Pairs

Author: remy727

README.md

@@ -190,6 +190,7 @@
 | 2316 | Count Unreachable Pairs of Nodes in an Undirected Graph | [Ruby](./algorithms/ruby/2316-count-unreachable-pairs-of-nodes-in-an-undirected-graph.rb) | Medium |
 | 2336 | Smallest Number in Infinite Set | [Ruby](./algorithms/ruby/2336-smallest-number-in-infinite-set.rb) | Medium |
 | 2348 | Number of Zero-Filled Subarrays | [Ruby](./algorithms/ruby/2348-number-of-zero-filled-subarrays.rb) | Medium |
+| 2352 | Equal Row and Column Pairs | [Ruby](./algorithms/ruby/2352-equal-row-and-column-pairs.rb) | Medium |
 | 2360 | Longest Cycle in a Graph | [Ruby](./algorithms/ruby/2360-longest-cycle-in-a-graph.rb) | Hard |
 | 2390 | Removing Stars From a String | [Ruby](./algorithms/ruby/2390-removing-stars-from-a-string.rb) | Medium |
 | 2405 | Count Days Spent Together | [Ruby](./algorithms/ruby/2405-optimal-partition-of-string.rb) | Medium |

algorithms/ruby/2352-equal-row-and-column-pairs.rb

@@ -0,0 +1,59 @@
+# frozen_string_literal: true
+
+# 2352. Equal Row and Column Pairs
+# https://leetcode.com/problems/equal-row-and-column-pairs
+# Medium
+
+=begin
+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
+=end
+
+# @param {Integer[][]} grid
+# @return {Integer}
+def equal_pairs(grid)
+  row_counts = Hash.new(0)
+  col_counts = Hash.new(0)
+  result = 0
+  grid.each { |el| row_counts[el] += 1 }
+  grid.size.times { |i| col_counts[grid.map { |el| el[i - 1] }] += 1 }
+
+  row_counts.each do |key, value|
+    if !col_counts[key].nil?
+      result += value * col_counts[key]
+    end
+  end
+  result
+end
+
+# **************** #
+#       TEST       #
+# **************** #
+
+require "test/unit"
+class Test_equal_pairs < Test::Unit::TestCase
+  def test_
+    assert_equal 1, equal_pairs([[3, 2, 1], [1, 7, 6], [2, 7, 7]])
+    assert_equal 3, equal_pairs([[3, 1, 2, 2], [1, 4, 4, 5], [2, 4, 2, 2], [2, 4, 2, 2]])
+  end
+end