LeetCode_sqrt(x)

class Solution {

public:

    int sqrt(int x) {

        // Start typing your C/C++ solution below

        // DO NOT write int main() function

    if(x < 0 ) return -1;

    if(x == 0) return 0;

    if(x >= 1 && x <= 3) return 1;

    

    double start = 2.0;

    double next =  0.5 *(start + x/start);

    while(abs(start * start - x) > 0.000001){

        start = next;

        next = 0.5 *(start + x/start);

    }

    

    return int(start);

    }

};

两种方法的详细分析： http://www.cnblogs.com/AnnieKim/archive/2013/04/18/3028607.html