LeetCode OJ:Sqrt(x)

1、二分法

class Solution {
public:
    int sqrt(int x) {
        if(x < 0) return -1;
        
        long long target = (long long)x;  
        long long left = 0;
        long long right = target;
        long long mid;
          
        while(left <= right){
            mid = left + (right - left) / 2;  
            
            if(mid * mid == target || (mid * mid < target && (mid + 1) * (mid + 1) > target)){  
               return (int)mid;  
            } else if(mid * mid < target){  
                left = mid + 1;  
            } else{  
                right = mid - 1;  
            }  
        }  
    }  
};

class Solution {
public:
    int sqrt(int x) {
        if(x < 0) return -1;
        
        double n=x;
        while(abs(n*n-x)>0.0001)n=(n+x/n)/2;
        
        return (int)n;
    }  
};

LeetCode OJ:Sqrt(x)

原文：http://blog.csdn.net/starcuan/article/details/18843641