A sample Hamilton path

Problem Description

Give you a Graph,you have to start at the city with ID zero.

 

Input

The first line is n(1<=n<=21) m(0<=m<=3)
The next n line show you the graph, each line has n integers.
The jth integers means the length to city j.if the number is -1 means there is no way. If i==j the number must be -1.You can assume that the length will not larger than 10000
Next m lines,each line has two integers a,b (0<=a,b<n) means the path must visit city a first.
The input end with EOF.

 

Output

For each test case,output the shorest length of the hamilton path.
If you could not find a path, output -1

 

Sample Input

 

Sample Output

 

Source

2010 ACM-ICPC Multi-University Training Contest（11）——Host by BUPT

 

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zhouzeyong

 

 1 #include<iostream>
 2 #include<cstdio>
 3 #include<cstring>
 4 #include<algorithm>
 5 using namespace std;
 6 
 7 int n,m;
 8 int dis[25][25];
 9 int f[2500000];
10 int dp[2500000][25];//dp[i][j]已访问的点集i 到达点i的最短hamilton 
11 const int MAX=3000000;
12 int ans;
13 
14 int main(){
15     int x=0,y=0;
16     while(scanf("%d%d",&n,&m)!=EOF){
17         memset(f,0,sizeof(f));
18         memset(dis,0,sizeof(dis));
19         memset(dp,0,sizeof(dp)); 
20         for(int i=0;i<n;i++)
21             for(int j=0;j<n;j++) scanf("%d",&dis[i][j]);
22         for(int i=1;i<=m;i++){
23             scanf("%d%d",&x,&y);
24             f[y]|=(1<<x);//观察了样例才发现 原来y可以多次出现 
25         }
26         for(int i=0;i<(1<<n);i++)
27             for(int j=0;j<n;j++)  dp[i][j]=MAX;
28         dp[1][0]=0;
29         for(int k=0;k<(1<<n);k++)
30             for(int i=0;i<n;i++)
31                 if(dp[k][i]!=MAX)
32                     for(int j=0;j<n;j++){
33                         if((dis[i][j]==-1)||(!(k&(1<<i)))||(k&(1<<j))||f[j]!=(k&f[j])) continue;//判断是否遍历过 
34                         dp[k|(1<<j)][j]=min(dp[k|(1<<j)][j],dp[k][i]+dis[i][j]);//f[k][i]->f[k+{j}][j] + dis(i, j) 
35                     }
36         ans=MAX;
37         for(int i=0;i<n;i++) ans=min(ans,dp[(1<<n)-1][i]);
38         if(ans==MAX) printf("-1\n");
39         else printf("%d\n",ans);
40     }
41     return 0;
42 }