[LeetCode] Problem 367 - Valid Perfect Square

Posted on | In ,

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

No.1

Input: 16

Output: true

No.2

Input: 14

Output: false

Code

1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
public boolean isPerfectSquare(int num) {
    int start = 1;
    int end = num;

    while (start <= end) {
        int mid = start + (end - start) / 2;
        float divide = num / (float) mid;

        if (mid == divide)
            return true;
        else if (mid > divide)
            end = mid - 1;
        else
            start = mid + 1;
    }

    return false;
}