有效的完全平方数

有效的完全平方数

class Solution {
    public boolean isPerfectSquare(int num) {
        int left = 0,right = num;
        while(left <= right){
            int mid = left + (right - left) / 2;
            long square = (long) mid * mid;
            if(square == num){
                return true;
            }else if(square > num){
                right = mid - 1;
            }else{
                left = mid + 1;
            }
        }
        return false;
    }
}