Leetcode: sqrt (x)

思路:

二分法

总结:

ull != int * int 

代码:

#include <iostream>
using namespace std;
class Solution {
public:
    int sqrt(int x) {
        unsigned long long l = 0, r = x, mid;
		unsigned long long multi;
		while(l < r ) {
			mid = (l+r) >> 1;
			multi = mid * mid;
			if(multi == x) {
				return mid;
			}else if(multi > x) {
				r = mid -1;
			}else {
				l = mid + 1;
			}
		}
		multi = l * l;
		if(multi > x)
			return l-1;
		else
	        return l;
    }
};

int main() {
	Solution solution;
	cout << solution.sqrt(2147395599) << endl;
	return 0;
}