0367: Valid Perfect Square

Author: golevy

0367-Valid_Perfect_Square/main.ts

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+// const num = 16;
+const num = 14;
+
+function isPerfectSquare(num: number): boolean {
+  if (num < 2) return true;
+
+  let left = 2;
+  let right = num >> 1;
+  while (left <= right) {
+    let mid = left + ((right - left) >> 1);
+    let div = num / mid;
+    if (mid === div) return true;
+    if (mid < div) {
+      left = mid + 1;
+    } else {
+      right = mid - 1;
+    }
+  }
+  return false;
+}
+
+console.time('isPerfectSquare');
+isPerfectSquare(num);
+console.timeEnd('isPerfectSquare');
+
+let result = isPerfectSquare(num);
+
+console.log(result);

0367-Valid_Perfect_Square/readme.md

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+# 367. Valid Perfect Square
+
+Given a positive integer num, return `true` <i>if `num` is a perfect square or</i> `false` otherwise.
+
+<b>A perfect square</b> is an integer that is the square of an integer. In other words, it is the product of some integer with itself.
+
+You must not use any built-in library function, such as `sqrt`.
+
+## Example 1:
+
+> <span style="color: white;">Input: </span>num = 16<br>
+> <span style="color: white;">Output: </span>true<br>
+> <span style="color: white;">Explanation: </span>We return true because 4 \* 4 = 16 and 4 is an integer.
+
+## Example 2:
+
+> <span style="color: white;">Input: </span>num = 14<br>
+> <span style="color: white;">Output: </span>false<br>
+> <span style="color: white;">Explanation: </span>We return false because 3.742 \* 3.742 = 14 and 3.742 is not an integer.
+
+## Constraints:
+
+- 1 <= num <= 2<sup>31</sup> - 1