[leetcode.com]算法题目 - Sqrt(x)

Implement int sqrt(int x).

Compute and return the square root of x.

 1 class Solution {

 2 public:

 3     int sqrt(int x) {

 4         // Start typing your C/C++ solution below

 5         // DO NOT write int main() function

 6         if(x<=0) return 0;

 7         if(x==1) return 1;

 8         int small=0;

 9         int large=x;

10         int temp=x/2;

11         while(small<large){

12             int a = x/temp;

13             int b = x/(temp+1);

14             if (a==temp) return a;

15             if (b==temp+1) return b;

16             if(temp<a && temp+1>b)

17                 return temp;

18             else if(temp<a && temp+1<b){

19                 small=temp+1;

20                 temp = (small+large)/2;

21             }else {

22                 large = temp;

23                 temp = (small+large)/2;

24             }

25         }

26         return -1;

27     }

28 };

我的答案

思路：需要在O(log n)时间内实现，并且注意用除法，防止两个int型的数相乘超过int的范围。