367. 有效的完全平方数

 1 bool isPerfectSquare(int num) 
 2 {
 3         int BinNum = num/2;
 4         
 5         int left = 0, right = BinNum;
 6         long long mid = (left + right) >> 1;
 7         if(num == 1)
 8         return true;
 9         if(num == 0)
10         return false;
11         while(left <= right)
12         {
13             if(mid * mid == num)
14             {
15                 return true;
16             }
17             else if(mid * mid > num)
18             {
19                 right = mid-1;
20                 mid = (left + right) >> 1;
21             }
22             else
23             {
24                 left = mid+1;
25                 mid = (left + right) >> 1;
26             }
27         }
28 
29         return false;
30 }