有代价的单源最短路径

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1. #include<iostream>  
2. #include<memory.h>  
3. #include<vector>  
4. using namespace std;  
5. #define N 505  
6. int map[N][N];  
7. vector<int> path,min_path;  
8. int bike[N];  
9. bool visit[N];  
10. #define INF 10000000  
11. int dest,n,req;//req:require  
12. int min_d,min_bring,min_back;  
13. int cur_d,cur_bring,cur_back;  
14.   
15. void dfs(int p)  
16. {  
17.     int i;  
18.     if(p==dest)  
19.     {  
20.         if(cur_d<min_d ||  
21.             cur_d==min_d && cur_bring < min_bring||  
22.             cur_d == min_d && cur_bring == min_bring && cur_back<min_back)  
23.         {  
24.             min_d = cur_d;  
25.             min_bring = cur_bring;  
26.             min_back = cur_back;  
27.             min_path = path;  
28.         }  
29.         return;  
30.     }  
31.     else  
32.     {  
33.         for(i=0;i<=n;i++)  
34.         {  
35.             if(!visit[i]&&map[p][i]!=INF)  
36.             {  
37.                 cur_d += map[p][i];  
38.                 visit[i] = true;  
39.                 path.push_back(i);  
40.                 if(bike[i]<req)  
41.                 {  
42.                     if(cur_back >= req-bike[i])  
43.                     {  
44.                         cur_back -= (req-bike[i]);  
45.                         dfs(i);  
46.                         cur_back += (req-bike[i]);  
47.                     }  
48.                     else  
49.                     {  
50.                         int t = cur_back;  
51.                         cur_bring += req-bike[i] - cur_back;  
52.                         cur_back = 0;  
53.                         dfs(i);  
54.                         cur_back = t;  
55.                         cur_bring -= req-bike[i] - cur_back;  
56.                     }  
57.                 }  
58.                 else  
59.                 {  
60.                     cur_back += bike[i]-req;  
61.                     dfs(i);  
62.                     cur_back -= (bike[i]-req);  
63.                 }                 
64.                 path.pop_back();  
65.                 visit[i] = false;  
66.                 cur_d-=map[p][i];  
67.             }  
68.         }  
69.     }  
70. }  
71.   
72. int main()  
73. {  
74.     int cm,m,i,j,t,a,b;  
75.     scanf("%d%d%d%d",&cm,&n,&dest,&m);  
76.     req = cm/2;  
77.     for(i=0;i<n;i++)  
78.         scanf("%d",&bike[i+1]);  
79.     memset(visit,false,sizeof(visit));  
80.     visit[0] = true;  
81.   
82.     for(i=0;i<=n;i++)  
83.         for(j=0;j<=n;j++)  
84.             map[i][j] = INF;  
85.   
86.     for(i=0;i<m;i++)  
87.     {  
88.         scanf("%d%d%d",&a,&b,&t);  
89.         if(map[a][b]>t)  
90.             map[a][b] = map[b][a] = t;  
91.     }  
92.     min_d = min_bring = min_back = INF;  
93.     cur_d = cur_bring = cur_back = 0;  
94.     path.push_back(0);  
95.     dfs(0);  
96.     cout<<min_bring<<" ";  
97.     printf("%d",min_path[0]);  
98.     for(i=1;i<min_path.size();i++)  
99.         printf("->%d",min_path[i]);  
100.     cout<<" "<<min_back<<endl;  
101.     return 0;  
102. }  

from: http://blog.csdn.net/abcjennifer/article/details/19830187