LeetCode 69. Sqrt(x) 时间复杂度（O(logn)）

时间复杂度（O(logn)），思想，二分查找

class Solution {
public:
    int mySqrt(int x) {
        if(x==0||x==1) return x;
        int starti = 1;
        int endi = x;
        while(endi>starti)
            if( x/((endi+starti)/2)<((endi+starti)/2))
                endi = ((endi+starti)/2);
            else if( x/((endi+starti)/2)>((endi+starti)/2)){
                if(starti == ((endi+starti)/2))return starti;
                starti = ((endi+starti)/2);
            }else 
                return (endi+starti)/2;
        return starti;  
    }
};

时间复杂度小于（O(logn)），思想，牛顿下山法

class Solution {
public:
    int mySqrt(int x) {
        if(x==0||x==1)return x;
        int result =x/2;
        while(!(resultx/(result+1) || result==x/result )){
            int mid_value = ((result+x/result)/2);
            if(mid_value==result)return result;
            result = mid_value;
        }
        return result; 
    }
};