Lintcode: Sqrt(X)

C++

class Solution {
public:
    /**
     * @param x: An integer
     * @return: The sqrt of x
     */
    int sqrt(int x) {
        // write your code here
        if (x<=1) {
            return x;
        }
        int left = 1;
        int right = x;
        while (left <= right) {
            int mid = left + ((right - left) >> 1);
            if (mid == x/mid) {
                return mid;
            }
            else if (mid < x/mid) {
                left = mid + 1;
            } else {
                right = mid - 1;
            }
        }
        return right;
    }
};