点和边 都很少，确定一个界限，爆搜即可。判断点到达注意一下，如果之前已经到了，就不用回溯了，如果之前没到过，要回溯。
1 #include <cstring> 2 #include <cstdio> 3 #include <string> 4 #include <iostream> 5 #include <algorithm> 6 #include <vector> 7 #include <queue> 8 using namespace std; 9 struct node 10 { 11 int a,b,c,p,r,next; 12 } edge[101]; 13 int first[21],t,minz; 14 int o[21],n; 15 void CL() 16 { 17 t = 1; 18 memset(first,-1,sizeof(first)); 19 memset(o,0,sizeof(o)); 20 } 21 void add(int a,int b,int c,int p,int r) 22 { 23 edge[t].a = a; 24 edge[t].b = b; 25 edge[t].c = c; 26 edge[t].p = p; 27 edge[t].r = r; 28 edge[t].next = first[a]; 29 first[a] = t ++; 30 } 31 void dfs(int x,int sum) 32 { 33 int i,v,s,z; 34 if(sum >= minz) 35 return ; 36 if(x == n) 37 { 38 minz = min(sum,minz); 39 return ; 40 } 41 for(i = first[x]; i != -1; i = edge[i].next) 42 { 43 v = edge[i].b; 44 s = edge[i].c; 45 z = 0; 46 if(o[s]) 47 { 48 if(o[v]) 49 z = 1; 50 else 51 o[v] = 1; 52 dfs(v,sum+edge[i].p); 53 if(z == 0) 54 o[v] = 0; 55 } 56 else 57 { 58 if(o[v]) 59 z = 1; 60 else 61 o[v] = 1; 62 dfs(v,sum+edge[i].r); 63 if(z == 0) 64 o[v] = 0; 65 } 66 } 67 return ; 68 } 69 int main() 70 { 71 int i,m,sum; 72 int a,b,c,p,r; 73 scanf("%d%d",&n,&m); 74 CL(); 75 sum = 0; 76 for(i = 1; i <= m; i ++) 77 { 78 scanf("%d%d%d%d%d",&a,&b,&c,&p,&r); 79 add(a,b,c,p,r); 80 sum += r; 81 } 82 minz = sum+1; 83 o[1] = 1; 84 dfs(1,0); 85 if(minz == sum+1) 86 printf("impossible "); 87 else 88 printf("%d ",minz); 89 return 0; 90 }