367. Valid Perfect Square

Posted 2020-08-09 咖啡中不塌缩的方糖

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

 public bool IsPerfectSquare(int num) {
        if(num == 0 || num == 1) return true;
        /*if(num == Int32.MaxValue) return false;
        int i = 0;
        int square = 0;
        while(square<=num)
        {
            square = i*i;
            if(num == square) return true;
            i++;
        }
        return false;*/
         for (int i = 1; i <= num / i; ++i) {
            if (i * i == num) return true;
        }
        return false;
    }

 

 

 

public bool IsPerfectSquare(int num) {
        if(num == 0 || num == 1) return true;
        //if(num == Int32.MaxValue) return false;
        long a = num/2;
        long square = a*a;
        while(square > num)
        {
                a = a/2;
                square = a*a;
        }
        
        for(long i = a;i<=a*2;i++)
        {
            if(i*i == num) return true;
        }
       return false;
    }