English
367. Valid Perfect Square
Problem Statement:
Given a positive integer num, write a function which returns True if num is a perfect square else False.
Follow up: Do not use any built-in library function such as sqrt
.
Example 1:
Input: num = 16
Output: true
Example 2:
Input: num = 14
Output: false
Constraints:
- 1 <= num <= 231 - 1
Solution:
java
public boolean isPerfectSquare(int num) {
if (num == 1)
return true;
long low = 1,
mid = 0,
high = num / 2;
while (low <= high) {
mid = low + (high - low) / 2;
if (mid * mid == num)
return true;
else if (mid * mid < num)
low = mid + 1;
else
high = mid - 1;
}
return false;
}
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