回溯

//求幂集
 1 #include<iostream>
 2 #include<cstdio>
 3 #include<cstdlib>
 4 #include<list>
 5 using namespace std;
 6 const int maxn = 10010;
 7 typedef list<int> List;
 8 List::iterator it;
 9 int a[maxn];
10 int n;
11 void Output(List l)
12 {
13     if(l.empty())
14         printf("φ");
15     else
16     {
17         printf("{");
18         for(it = l.begin(); it != l.end(); it++)
19         {
20             if(it != l.begin()) printf(" ");
21             printf("%d", *it);
22         }
23         printf("}, ");
24     }
25 }
26 
27 void GetPowerSet(int i, List A, List& B)
28 {//求n个元素的集合A的幂集，进入函数时已对A中前i-1个元素作了取舍处理，现对第i个元素进行取舍处理
29     //线性表A表示集合A， 线性表B表示幂集的一个元素
30     //初始调用PowerSet(1, A, B);    B为空表
31     if(i>n)//输出幂集的一个元素
32     {
33         Output(B);
34     }
35     else
36     {
37         int x = a[i];
38         B.push_back(x);
39         GetPowerSet(i+1, A, B);
40         B.pop_back();
41         GetPowerSet(i+1, A, B);
42     }
43 }
44 int main()
45 {
46     scanf("%d", &n);
47     for(int i = 1; i <= n; i++)        a[i] = i;
48     List A(a, a+n), B;
49     printf("{ ");
50     GetPowerSet(1, A, B);
51     printf(" }");
52     return 0;
53 }

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 //八皇后问题
 1 #include<iostream>
 2 #include<cstdio>
 3 #include<cstdlib>
 4 #include<cstring>
 5 using namespace std;
 6 const int maxn = 1001;
 7 int n;
 8 int C[maxn];
 9 bool status[3][maxn];
10 void Output()
11 {
12     for(int i = 0; i < n; i++)
13     {
14         if(i)   printf(" ");
15         printf("%d", C[i]);
16     }
17     printf("
");
18 }
19 
20 void Trial(int i)
21 {
22     if(i == n)
23     {
24         Output();
25 //        tot++;
26     }
27     else
28     {
29         for(int j = 0; j < n; j++)
30         {
31             if(!status[0][j] && !status[1][i+j] && !status[2][(i-j+n)])
32             {
33                 C[i] = j;
34                 status[0][j] = status[1][i+j] = status[2][(i-j+n)] = 1;
35                 Trial(i+1);
36                 status[0][j] = status[1][i+j] = status[2][(i-j+n)] = 0;
37             }
38         }
39     }
40 }
41 
42 int main()
43 {
44     memset(C, 0, sizeof(C));
45     memset(status, 0, sizeof(status));
46     scanf("%d", &n);
47     Trial(0);
48 
49     return 0;
50 }