The 3n+1 problem

一道很经典的题，各大OJ上面都有，经典的递归设计。

 

 

 1 #include <stdio.h>
 2 #include <string.h>
 3  #define SWP(x,y,t) ((t)=(x),(x)=(y),(y)=(t))
 4  #define NL 10010
 5 
 6  int cyl[NL];
 7 
 8  int f(int k)
 9 {
10     if (k == 1) return 1;
11     if (k<NL && cyl[k]) return cyl[k];
12     if (k&1) {
13         if (k<NL) return cyl[k] = f(3*k+1) + 1; //注意不要越界
14         else return f(3*k+1) + 1;
15     }else {
16         if (k<NL) return cyl[k] = f(k/2) + 1;
17         else return f(k/2) + 1;
18     }
19 }
20 //打表计算
21  void getCyl()
22 {
23     memset(cyl, 0, sizeof(cyl));
24     for (int i=1; i<NL; i++) {
25         if (cyl[i]) continue;
26         cyl[i] = f(i);
27     }
28 }
29 
30  int main()
31 {
32     getCyl();
33     int a, b, t;
34     while (scanf("%d%d", &a, &b) != EOF) {
35         printf("%d %d ", a, b);
36         if (a > b) SWP(a,b,t);
37         int max = 0;
38         for (int i=a; i<=b; i++) {
39             if (cyl[i] > max) max = cyl[i];
40         }
41         printf("%d\n", max);
42     }
43     return 0;
44 }
45 
46

 

 

posted @ 2010-05-03 10:01  superbin  阅读(367)  评论(0)    收藏  举报