http://poj.org/problem?id=3114
缩点+DIJK 注意缩点之后有重边啊 floyd会TLE
1 #include <iostream> 2 #include<cstring> 3 #include<cstdio> 4 #include<stdlib.h> 5 #include<algorithm> 6 #include<stack> 7 #define N 510 8 #define M 301000 9 #define INF 0xfffffff 10 using namespace std; 11 struct node 12 { 13 int u,v,next,w; 14 }edge[M]; 15 int t,low[N],pre[N],sccno[N],head[N],scc,dep,ww[N][N],vis[N],dis[N]; 16 int o[N][N]; 17 void init() 18 { 19 t = 0; 20 memset(head,-1,sizeof(head)); 21 } 22 void add(int u,int v,int w) 23 { 24 edge[t].u =u; 25 edge[t].v = v; 26 edge[t].w = w; 27 edge[t].next = head[u]; 28 head[u] = t++; 29 } 30 stack<int>s; 31 void dfs(int u) 32 { 33 low[u] = pre[u] = ++dep; 34 s.push(u); 35 for(int i = head[u] ; i!=-1 ; i = edge[i].next) 36 { 37 int v = edge[i].v; 38 if(!pre[v]) 39 { 40 dfs(v); 41 low[u] = min(low[u],low[v]); 42 } 43 else if(!sccno[v]) 44 low[u] = min(low[u],pre[v]); 45 } 46 if(low[u]==pre[u]) 47 { 48 scc++; 49 for(;;) 50 { 51 int x = s.top();s.pop(); 52 sccno[x] = scc; 53 if(x==u)break; 54 } 55 } 56 } 57 void find_scc(int n) 58 { 59 scc=0;dep=0; 60 memset(low,0,sizeof(low)); 61 memset(pre,0,sizeof(pre)); 62 memset(sccno,0,sizeof(sccno)); 63 for(int i = 1; i <= n ; i++) 64 if(!pre[i]) 65 dfs(i); 66 } 67 int dijk(int st,int en,int n) 68 { 69 int i,j,k,mi; 70 memset(vis,0,sizeof(vis)); 71 for(i = 1; i <= n ; i++) 72 dis[i] = o[st][i]; 73 dis[st] = 0; 74 for(i = 1 ;i <= n ; i++) 75 { 76 mi = INF; 77 for(j = 1; j <= n ; j++) 78 if(!vis[j]&&dis[j]<=mi) 79 mi = dis[k=j]; 80 vis[k] = 1; 81 for(j = 1; j <= n ; j++) 82 if(dis[j]>o[k][j]+dis[k]) 83 dis[j] = o[k][j]+dis[k]; 84 } 85 return dis[en]; 86 } 87 int main() 88 { 89 int i,j,n,m,k,a,b,c,g; 90 while(cin>>n>>m) 91 { 92 if(n==0&&m==0) 93 break; 94 memset(ww,0,sizeof(ww)); 95 init(); 96 for(i =1; i <= m ;i++) 97 { 98 scanf("%d%d%d",&a,&b,&c); 99 add(a,b,c); 100 } 101 find_scc(n); 102 for(i = 1; i <= n ; i++) 103 for(j = 1; j <= n ;j++) 104 o[i][j] = INF; 105 for(i = 1; i <= scc ; i++) 106 o[i][i] = 0; 107 for(i = 0; i < t ; i++) 108 { 109 int u = edge[i].u,v = edge[i].v; 110 if(sccno[u]!=sccno[v]) 111 { 112 o[sccno[u]][sccno[v]] = min(o[sccno[u]][sccno[v]],edge[i].w);//没算重的之前 WA惨了 113 } 114 } 115 scanf("%d",&k); 116 while(k--) 117 { 118 scanf("%d%d",&a,&b); 119 int xx = dijk(sccno[a],sccno[b],scc); 120 if(xx==INF) 121 printf("Nao e possivel entregar a carta "); 122 else 123 cout<<xx<<endl; 124 } 125 puts(""); 126 } 127 return 0; 128 }