实现sqrt()函数

方法一：

  int mySqrt(int x) {

        if(x == 0)
         {
           return 0;
         }        
         int ans = exp(0.5*log(x));
         int k = ans+1;
         //int r = k*k;
         if((long long) k*k <=x)
         {
              return k;
         }
         else
         {
              return ans;
         }
    }

　　

方法二：二分查找

  int mySqrt(int x) {
      int l = 0, r = x, ans = -1;
        while (l <= r) {
            int mid = l + (r - l) / 2;
            if ((long long)mid * mid <= x) {
                ans = mid;
                l = mid + 1;
            }
            else {
                r = mid - 1;
            }
        }
        return ans;
    }