✨ number of equivalent domino pairs

Author: tangweikun

src/1128-number-of-equivalent-domino-pairs/index.js

@@ -1,36 +1,16 @@
-/**
- * @param {number[][]} dominoes
- * @return {number}
- */
-
-var numEquivDominoPairs = function(dominoes) {
-  const map = {};
+var numEquivDominoPairs = function (dominoes) {
+  const arr = Array(100).fill(0);
   let res = 0;
 
-  for (let pair of dominoes) {
-    const foo = pair[0] * 10 + pair[1];
-    const bar = pair[1] * 10 + pair[0];
-    if (foo === bar) {
-      map[foo] = ~~map[foo] + 1;
-    } else {
-      map[foo] = ~~map[foo] + 1;
-      map[bar] = ~~map[bar] + 1;
-    }
-  }
+  for (const domino of dominoes) {
+    const val = Math.min(
+      domino[0] * 10 + domino[1],
+      domino[1] * 10 + domino[0]
+    );
 
-  for (let key of Object.keys(map)) {
-    if (map[key] > 1) {
-      if (String(key)[0] === String(key)[1]) {
-        res += (map[key] * (map[key] - 1)) / 2;
-      } else {
-        res += (map[key] * (map[key] - 1)) / 4;
-      }
-    }
+    res += arr[val];
+    arr[val]++;
   }
 
   return res;
 };
-
-console.log(
-  numEquivDominoPairs([[1, 1], [2, 2], [1, 1], [1, 2], [1, 2], [1, 1]]),
-);

src/1128-number-of-equivalent-domino-pairs/pro.js

@@ -0,0 +1,22 @@
+/**
+ * @param {number[][]} dominoes
+ * @return {number}
+ */
+var numEquivDominoPairs = function (dominoes) {
+  const hash = {};
+  let count = 0;
+  for (let i = 0; i < dominoes.length; i++) {
+    const str = dominoes[i].sort().toString();
+    !hash[str] && (hash[str] = 0);
+    hash[str]++;
+  }
+
+  const values = Object.values(hash);
+  for (let j = 0; j < values.length; j++) {
+    if (values[j] > 1) {
+      count += (values[j] * (values[j] - 1)) / 2;
+    }
+  }
+
+  return count;
+};