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;
    }
}