经典问题：哈密尔顿路径 DP~

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 1 #include <cstdio>
 2 #include <cstring>
 3 
 4  #define MIN(a,b) (a < b ? a : b)
 5 
 6  using namespace std;
 7 
 8 const int NC = 20;
 9 const int INF = (1 << 20);
10 
11 int dp[1<<NC][NC];
12 
13 int limit[NC];
14 int length[NC][NC];
15 
16 int main()
17 {
18     int nv;
19     int nl;
20     int va;
21     int vb;
22 
23     while (scanf("%d %d",&nv,&nl) != EOF)
24     {
25         memset(limit,0,sizeof(limit));
26 
27         for (int i = 0;i < nv;i++)
28             for (int j = 0;j < nv;j++)
29                 scanf("%d",&length[i][j]);
30 
31         for (int i = 0;i < nl;i++)
32         {
33             scanf("%d %d",&va,&vb);
34             limit[vb] |= (1 << va);
35         }
36 
37         int lim = (1 << nv);
38         for (int i = 0;i < lim;i++)
39             for (int j = 0;j < nv;j++)
40                 dp[i][j] = INF;
41 
42         dp[1][0] = 0;
43 
44         for (int i = 1;i < lim;i++)
45             for (int j = 0;j < nv;j++)
46                 for (int k = 0;k < nv;k++)
47                     if (!(i & (1 << k)) && length[j][k] != -1 && (i & limit[k]) == limit[k])
48                         dp[i|(1<<k)][k] = MIN(dp[i|(1<<k)][k],dp[i][j] + length[j][k]);
49 
50         int ans = (1 << 20);
51         for (int i = 0;i < nv;i++)
52         {
53             int tmp = dp[lim-1][i];
54             if (ans > tmp)
55                 ans = tmp;
56         }
57         printf("%d\n",ans == INF ? -1 : ans);
58     }
59     return 0;
60 }