69. Sqrt(x)(二分查找)

Implement int sqrt(int x).

Compute and return the square root of x, where x is guaranteed to be a non-negative integer.

Since the return type is an integer, the decimal digits are truncated and only the integer part of the result is returned.

Example 1:

Input: 4
Output: 2

Example 2:

Input: 8
Output: 2
Explanation: The square root of 8 is 2.82842..., and since
             the decimal part is truncated, 2 is returned.

 class Solution {
     public int mySqrt(int x) {
         long lo = 0;
         long hi = x/2+1;

         while(lo<=hi){
              long mid = (hi-lo)/2+lo;
             if(mid*mid==x)
                 return (int)mid;
             else if(mid*mid>x)
                 hi = mid-1;
             else
                 lo = mid+1;

         }
         return (int)lo-1;
     }
 }