367. 有效的完全平方数

Author: w2xi

README.md

@@ -82,6 +82,7 @@
 |344|[反转字符串](https://leetcode-cn.com/problems/reverse-string/)|[JavaScript](./algorithms/reverse-string.js)|Easy|
 |349|[两个数组的交集](https://leetcode-cn.com/problems/intersection-of-two-arrays/)|[JavaScript](./algorithms/intersection-of-two-arrays.js)|Easy|
 |350|[两个数组的交集 II](https://leetcode-cn.com/problems/intersection-of-two-arrays-ii/)|[JavaScript](./algorithms/intersection-of-two-arrays-ii.js)|Easy|
+|367|[有效的完全平方数](https://leetcode.cn/problems/valid-perfect-square/)|[JavaScript](./algorithms/valid-perfect-square.js)|Easy|
 |383|[赎金信](https://leetcode.cn/problems/ransom-note/)|[JavaScript](./algorithms/ransom-note.js)|Easy|
 |387|[字符串中的第一个唯一字符](https://leetcode-cn.com/problems/first-unique-character-in-a-string/)|[JavaScript](./algorithms/first-unique-character-in-a-string.js)|Easy|
 |389|[找不同](https://leetcode.cn/problems/find-the-difference/)|[JavaScript](./algorithms/find-the-difference.js)|Easy|

algorithms/valid-perfect-square.js

@@ -0,0 +1,27 @@
+/**
+ * @param {number} num
+ * @return {boolean}
+ */
+var isPerfectSquare = function (num) {
+  let left = 1;
+  let right = num;
+
+  // num = 9
+  // 1 9 mid = 5
+  // 1 4 mid = 2
+  // 3 4 mid = 3
+
+  while (left <= right) {
+    let mid = Math.floor((left + right) / 2);
+
+    if (mid * mid < num) {
+      left = mid + 1;
+    } else if (mid * mid > num) {
+      right = mid - 1;
+    } else {
+      return true;
+    }
+  }
+
+  return false;
+};