数字全排列

 题解：

 　　一条路走到头，然后再回头

　　vis数组来标记已走过的点，a数组来存数字

 1 #include <bits/stdc++.h>
 2 using namespace std;
 3 int n;
 4 bool vis[20];
 5 int a[20];
 6 
 7 void dfs(int x)
 8 {
 9     if (x > n)
10     {
11         for (int i = 1; i < n; ++i)
12             cout << a[i] << " ";
13         cout << a[n] << " " << endl;
14         return; // 回溯
15     }
16 
17     for (int i = 1; i <= n; ++i)
18     {
19         if (!vis[i])
20         {
21             vis[i] = 1;
22             a[x] = i;
23             dfs(x + 1);
24             vis[i] = 0;
25         }
26     }
27     return; // 回溯
28 }
29 
30 int main()
31 {
32     cin >> n;
33     dfs(1);
34     return 0;
35 }

以下为python代码：

 1 n = int(input())
 2 vis = [False] * (n + 1)
 3 a = [0] * (n + 1)
 4 
 5 
 6 def dfs(x):
 7     if x > n:
 8         for i in range(1, n + 1):
 9             print(a[i], end=' ')
10         print()
11         return
12 
13     for i in range(1, n + 1):
14         if not vis[i]:
15             vis[i] = 1
16             a[x] = i
17             dfs(x + 1)
18             vis[i] = 0
19 
20 
21 dfs(1)