lintcode:x的平方根

x的平方根

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lintcode 题目链接

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class Solution {
public:
    /**
     * @param x: An integer
     * @return: The sqrt of x
     */
    int binary_search(long  l,long  r, long &x){
        while(l<=r)
        {
            long mid=(l+r)>>1;
            long long ans1=mid*mid;
            long long ans2=(mid+1)*(mid+1);
            if(ans1>x)
                r=mid-1;
            else if(ans1<x && ans2<=x) 
                l=mid+1;
            else if(ans1<=x &&ans2>x)
                return mid;
        }
        return 0;
    }
    int sqrt(int x) {
        // write your code here
        long r=x;
        if(r>3) r>>1;
        return binary_search(1,r,r);
    }
};