Create 1128-number-of-equivalent-domino-pairsnumber-of-equivalent-domino-pairs.js

Author: everthis

1128-number-of-equivalent-domino-pairsnumber-of-equivalent-domino-pairs.js

@@ -0,0 +1,34 @@
+/**
+ * @param {number[][]} dominoes
+ * @return {number}
+ */
+const numEquivDominoPairs = function(dominoes) {
+  const hash = {}
+  for (let dom of dominoes) {
+    const [a, b] = dom
+    const key = `${a},${b}`, alterKey = `${b},${a}`
+    if (hash[key] == null && hash[alterKey] == null) {
+      hash[key] = 1
+    } else {
+      if(hash[key] != null) hash[key] += 1
+      else hash[alterKey] += 1
+    }
+  }
+
+  let res = 0
+
+  Object.keys(hash).forEach(k => {
+    if(hash[k] > 1) res += sum(hash[k])
+  })
+
+  return res
+};
+
+function sum(n) {
+  let res = 0
+  while(n > 1) {
+    res += n - 1
+    n--
+  }
+  return res
+}