[leetcode-69-Sqrt(x)]

Implement int sqrt(int x).

Compute and return the square root of x.

思路：

 二分法。牛顿迭代法。

int mySqrt(int x)
     {
        if (x == 0) return 0;
         int left = 1, right = INT_MAX;
         while (1)
         {
             int mid = left + (right - left) / 2;
             if (mid * mid > x)
             {
                 right = mid - 1;
             }
             else
             {
                 if((mid + 1)*(mid+1) > x)
                 {
                     return mid;
                 }
                 left = mid + 1;
             }
         }
     }

 int newton(int x)
     {
         if (x == 0) return 0;         
         double ans = x;
         while (abs(pow(ans, 2) - x) > 0.001)
         {
             ans = (ans + x / ans) / 2;
         }
         return ans;
     }

参考：

https://discuss.leetcode.com/topic/8689/newton-s-iterative-method-in-c