Sqrt(x)

Discussion

二分查找，注意溢出问题。

Solution

int sqrt(int x) {
        if (0 == x) return 0;
        int left = 1, right = x, ans;
        while (left <= right) {
            int mid = left + (right - left) / 2;
            if (mid <= x / mid) {
                left = mid + 1;
                ans = mid;
            } else {
                right = mid - 1;
            }
        }
        return ans;
    }

right = x/2 + 1也可以。不能比较(mid*mid <=x )因为可能溢出。