LeetCode 069 Sqrt(x) 求平方根

Implement int sqrt(int x).
Compute and return the square root of x.
x is guaranteed to be a non-negative integer.
Example 1:
Input: 4
Output: 2
Example 2:
Input: 8
Output: 2
Explanation: The square root of 8 is 2.82842..., and since we want to return an integer, the decimal part will be truncated.
（1）暴力搜索

class Solution {
public:
    int mySqrt(int x) {
        if(x<=0)
            return x;
        int begin=1;
        int end=x;
        int mid=0;
        while(begin<=end)
        {
            mid=(begin+end)/2;
            if(mid==x/mid)
                return mid;
            else if(mid<x/mid)
                begin=mid+1;
            else
                end=mid-1;
        }
        return end;
    }
};

（2）牛顿迭代

class Solution {
public:
    int mySqrt(int x)
    {
        long long v=x;
        while(v*v>x)
            v=(v+x/v)>>1;
        return v;
    }
};