思路：
搜索。注意点和边都有可能经过多次。
实现：
1 #include <iostream> 2 #include <cstdio> 3 #include <vector> 4 using namespace std; 5 const int MAXN = 15, INF = 0x3f3f3f3f; 6 int n, m; 7 struct edge 8 { 9 int to, c, p, r; 10 }; 11 vector<edge> G[MAXN]; 12 int vis[MAXN]; 13 14 int dfs(int now) 15 { 16 if (now == n) 17 return 0; 18 int ans = INF; 19 for (int i = 0; i < G[now].size(); i++) 20 { 21 if (vis[G[now][i].to] > 3) continue; 22 vis[G[now][i].to]++; 23 int x = dfs(G[now][i].to) + G[now][i].r; 24 ans = min(ans, x); 25 int y = INF; 26 if (vis[G[now][i].c]) 27 y = dfs(G[now][i].to) + G[now][i].p; 28 ans = min(ans, y); 29 vis[G[now][i].to]--; 30 } 31 return ans; 32 } 33 34 int main() 35 { 36 cin >> n >> m; 37 int a, b, c, p, r; 38 for (int i = 0; i < m; i++) 39 { 40 cin >> a >> b >> c >> p >> r; 41 G[a].push_back(edge{b, c, p, r}); 42 } 43 vis[1] = true; 44 int ans = dfs(1); 45 if (ans == INF) puts("impossible"); 46 else cout << ans << endl; 47 return 0; 48 }