add 1128

fishercoder1534 · fishercoder1534 · commit e3e2475658be · 2019-12-05T06:39:28.000-08:00
diff --git a/README.md b/README.md
@@ -26,6 +26,7 @@ _If you like this project, please leave me a star._ &#9733;
 |1150|[Check If a Number Is Majority Element in a Sorted Array](https://leetcode.com/problems/check-if-a-number-is-majority-element-in-a-sorted-array/)|[Solution](../master/src/main/java/com/fishercoder/solutions/_1150.java) | | | |Easy||
 |1137|[N-th Tribonacci Number](https://leetcode.com/problems/n-th-tribonacci-number/)|[Solution](../master/src/main/java/com/fishercoder/solutions/_1137.java) | O(n) | O(n) | |Easy||
 |1134|[Armstrong Number](https://leetcode.com/problems/armstrong-number/)|[Solution](../master/src/main/java/com/fishercoder/solutions/_1134.java) |  |  | [:tv:](https://www.youtube.com/watch?v=HTL7fd4HPf4)|Easy||
+|1128|[Number of Equivalent Domino Pairs](https://leetcode.com/problems/number-of-equivalent-domino-pairs/)|[Solution](../master/src/main/java/com/fishercoder/solutions/_1128.java) |  |  | |Easy||
 |1122|[Relative Sort Array](https://leetcode.com/problems/relative-sort-array/)|[Solution](../master/src/main/java/com/fishercoder/solutions/_1122.java) | O(n) | O(n) | |Easy||
 |1170|[Compare Strings by Frequency of the Smallest Character](https://leetcode.com/problems/compare-strings-by-frequency-of-the-smallest-character/)|[Solution](../master/src/main/java/com/fishercoder/solutions/_1170.java) | | | |Easy||
 |1119|[Remove Vowels from a String](https://leetcode.com/problems/remove-vowels-from-a-string/)|[Solution](../master/src/main/java/com/fishercoder/solutions/_1119.java) | | | [:tv:](https://www.youtube.com/watch?v=6KCBrIWEauw)|Easy||
diff --git a/src/main/java/com/fishercoder/solutions/_1128.java b/src/main/java/com/fishercoder/solutions/_1128.java
@@ -0,0 +1,38 @@
+package com.fishercoder.solutions;
+
+import java.util.HashMap;
+import java.util.Map;
+
+/**
+ * 1128. Number of Equivalent Domino Pairs
+ *
+ * Given a list of dominoes, dominoes[i] = [a, b] is equivalent to dominoes[j] = [c, d] if and only if either (a==c and b==d), or (a==d and b==c) - that is, one domino can be rotated to be equal to another domino.
+ * Return the number of pairs (i, j) for which 0 <= i < j < dominoes.length, and dominoes[i] is equivalent to dominoes[j].
+ *
+ * Example 1:
+ *
+ * Input: dominoes = [[1,2],[2,1],[3,4],[5,6]]
+ * Output: 1
+ *
+ * Constraints:
+ * 1 <= dominoes.length <= 40000
+ * 1 <= dominoes[i][j] <= 9
+ * */
+public class _1128 {
+    public static class Solution1 {
+        public int numEquivDominoPairs(int[][] dominoes) {
+            int m = dominoes.length;
+            Map<Integer, Integer> map = new HashMap<>();
+            int count = 0;
+            for (int i = 0; i < m; i++) {
+                int smaller = Math.min(dominoes[i][0], dominoes[i][1]);
+                int bigger = Math.max(dominoes[i][0], dominoes[i][1]);
+                int key = smaller * 10 + bigger;
+                count += map.getOrDefault(key, 0);
+                map.put(key, map.getOrDefault(key, 0) + 1);
+            }
+            return count;
+        }
+
+    }
+}
diff --git a/src/test/java/com/fishercoder/_1128Test.java b/src/test/java/com/fishercoder/_1128Test.java
@@ -0,0 +1,28 @@
+package com.fishercoder;
+
+import com.fishercoder.solutions._1128;
+import org.junit.BeforeClass;
+import org.junit.Test;
+
+import static junit.framework.TestCase.assertEquals;
+
+public class _1128Test {
+    private static _1128.Solution1 solution1;
+    private static int[][] dominoes;
+
+    @BeforeClass
+    public static void setup() {
+        solution1 = new _1128.Solution1();
+    }
+
+    @Test
+    public void test1() {
+        dominoes = new int[][]{
+                {1, 2},
+                {2, 1},
+                {3, 4},
+                {5, 6}
+        };
+        assertEquals(1, solution1.numEquivDominoPairs(dominoes));
+    }
+}
