Sqrt(x)

Implement int sqrt(int x).

Compute and return the square root of x.

思路：

使用二分。为了减少搜索范围，将上界定位最大的整数的开方，也避免了整数越界的情况。另外在第9行分别先除2再相加，也是避免越界。

代码：

 1     int border(int a){
 2         if(a < 46341)
 3             return a;
 4         return 46341;
 5     }
 6     int sqrt(int left, int right, int x){        
 7         if(left == right)
 8             return left-1;
 9         int middle = border(left/2 + right/2);
10         double t = middle*middle;
11         if(t < x){
12             return sqrt(middle+1, right, x);
13         }
14         else if(t > x){
15             return sqrt(left, middle, x);
16         }
17         else
18             return middle;
19     }
20     int sqrt(int x) {
21         // IMPORTANT: Please reset any member data you declared, as
22         // the same Solution instance will be reused for each test case.
23         if(x == 0 || x == 1)
24             return x;
25         return sqrt(1, border(x), x);
26     }

 

posted on 2013-11-10 00:51  waruzhi  阅读(287)  评论(0)  编辑  收藏  举报

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