Valid Perfect Square

0367-Valid-Perfect-Square.py

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+'''
+Given a positive integer num, write a function which returns True if num is a perfect square else False.
+
+Note: Do not use any built-in library function such as sqrt.
+
+Example 1:
+
+Input: 16
+Output: true
+Example 2:
+
+Input: 14
+Output: false
+'''
+class Solution:
+    def isPerfectSquare(self, num: int) -> bool:
+        start, end = 0, num
+        while start <= end:
+            mid = (start+end)//2
+            square = mid*mid
+            if square == num:
+                return True
+            elif square > num:
+                end = mid - 1
+            else:
+                start = mid + 1
+        return False