LEETCODE--Valid Perfect Square

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

Returns: True

Example 2:

Input: 14

Returns: False

class Solution {
public:
bool isPerfectSquare(int num) {
int begin = 1;
int end = num;
while(begin <= end){
long int x = (begin + end ) / 2;
if(x * x == num)
return true;
if(x * x < num)
begin = x + 1;
if(x * x > num)
end = x - 1;
}
return false;
}
};