20250504 finished.

src/problem/mod.rs

@@ -632,3 +632,5 @@ mod p2071_maximum_number_of_tasks_you_can_assign;
 mod p838_push_dominoes;
 
 mod p1007_minimum_domino_rotations_for_equal_row;
+
+mod p1128_number_of_equivalent_domino_pairs;

src/problem/p1128_number_of_equivalent_domino_pairs.rs

@@ -0,0 +1,58 @@
+/**
+ * [1128] Number of Equivalent Domino Pairs
+ */
+pub struct Solution {}
+
+// submission codes start here
+use std::collections::HashMap;
+
+impl Solution {
+    pub fn num_equiv_domino_pairs(dominoes: Vec<Vec<i32>>) -> i32 {
+        let mut map = HashMap::new();
+        let mut result = 0;
+
+        for card in dominoes.iter() {
+            let sum = card[0] * 10 + card[1];
+
+            if let Some(count) = map.get(&sum) {
+                result += *count;
+            }
+
+            let entry = map.entry(sum).or_insert(0);
+            *entry += 1;
+
+            let reverse_sum = card[1] * 10 + card[0];
+            if reverse_sum != sum {
+                let entry = map.entry(card[1] * 10 + card[0]).or_insert(0);
+                *entry += 1;
+            }
+        }
+
+        result
+    }
+}
+
+// submission codes end
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[test]
+    fn test_1128() {
+        assert_eq!(
+            1,
+            Solution::num_equiv_domino_pairs(vec![vec![1, 2], vec![2, 1], vec![3, 4], vec![5, 6]])
+        );
+        assert_eq!(
+            3,
+            Solution::num_equiv_domino_pairs(vec![
+                vec![1, 2],
+                vec![1, 2],
+                vec![1, 1],
+                vec![1, 2],
+                vec![2, 2]
+            ])
+        );
+    }
+}