请老师指点 C语言的35课课后题第一题的递归思路
本帖最后由 wow7jiao 于 2018-7-13 10:43 编辑http://bbs.fishc.org/thread-79184-1-4.html 原帖地址
01.#include <stdio.h>
02.
03.#define MAX_NUM 64
04.
05.int schedule;
06.
07.int arrange(int begin, int num);
08.
09.int arrange(int begin, int num)
10.{
11. int i, j;
12.
13. if (num == 2)
14. {
15. schedule = begin;
16. schedule = begin + 1;
17. schedule = begin + 1;
18. schedule = begin;
19. return 0;
20. }
21.
22. arrange(begin, num/2); <----我输入8个队伍，这里begin=1，num/2=4
23. arrange(begin + num/2, num/2);<----这里是不是being=1+8/2=5，num/2=8/2=4
24.
25. for (i = begin + num/2; i < begin + num; i++)
26. {
27. for (j = num/2 + 1; j <= num; j++)
28. {
29. schedule = schedule;
30. }
31. }
32.
33. for (i = begin; i < begin + num/2; i++)
34. {
35. for (j = num/2 + 1; j <= num; j++)
36. {
37. schedule = schedule;
38. }
39. }
40.}
41.
42.int main(void)
43.{
44. int num, i, j;
45.
46. printf("请输入参赛的队伍数量：");
47. scanf("%d", &num);
48.
49. // 检查num是否2的N次方
50. // 注意，这里是&，不是&&
51. // &是按位与操作，1&1==1，0&1==0，0&0 == 0
52. if (num & num - 1)
53. {
54. printf("参数队伍的数量必须是2的N次方！\n");
55. return -1;
56. }
57.
58. arrange(1, num);
59.
60. printf("编 号");
61.
62. for (i = 1; i < num; i++)
63. {
64. printf("\t第%d天", i);
65. }
66.
67. putchar('\n');
68.
69. for (i = 1; i <= num; i++)
70. {
71. for (j = 1; j <= num; j++)
72. {
73. printf("%3d\t", schedule);
74. }
75. putchar('\n');
76. }
77.
78. return 0;
79.}
如图递归应该这样的。
22. arrange(begin, num/2);
23. arrange(begin + num/2, num/2
2个递归的嵌套请问流程是怎么样的？ 楼主可以在用IDE编程时进行debug，观察call stack调用栈的使用情况 void draw(int i,int j){
printf("%d%d\n",i,j);
if(j==2){
}
else{
draw(i,j/2);
draw(i/2+k,j/2);
}
}
i,j随便等于一个值，开始执行程序，当j不等于2时，执行else中的draw(i,j/2);
就是递归开始，直到j等于2，开始返回函数，再执行else中的draw(i/2+k,j/2);
递归又开始，直到j等于2，开始返回函数。。。大概是这个流程。 本帖最后由 wow7jiao 于 2018-7-14 15:31 编辑
arrange(begin, num/2);
schedule = 1, shchdule = 2
schedule = 2, shchdule = 1
arrange(begin + num/2, num/2);
schedule = 3, shchdule = 4
schedule = 4, shchdule = 3
//这是双递归最后退出时的结果，下面的2个for循环应该是最先填充。
本帖最后由 wow7jiao 于 2018-7-14 16:26 编辑
2个for 循环是平行的，可以前后调换
--------------------------------------------------------
arrange(begin,num/2);
num = 8
for(i = 1; i < 5; i++)
for(j = 5; j <= 8; j++)
schedule = schedule
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=
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=
=
----------------------------------------------------------
arrange(begin + num/2, num/2);
num = 8
for(i = 5, i < 9; i++)
for(j = 5; j <= 8; j++)
schedule = schedule
schedule = schedule
schedule = schedule
schedule = schedule
schedule = schedule
schedule = schedule
schedule = schedule
schedule = schedule
schedule = schedule
schedule = schedule
schedule = schedule
schedule = schedule
schedule = schedule
schedule = schedule
schedule = schedule
schedule = schedule
这是顺序
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