POJ countries in War 3114

Main topic:

Given some cities, and then give some road letters to send letters, A,B,H representative to send letter a city to B city needs h hours.

If not directly can be sent to, you can first through another city to arrive, such as a, B can send a letter, b,c can send a letter, then, A,c can also send a letter.

Among the two cities, if you can send letters to each other, then the two cities belong to a country, the letter can be emailed, so the time required is 0.

There are k queries in the topic, enter a, B, ask the minimum amount of time to send a letter

Topic Analysis:

First the strong unicom and then the composition to find the shortest way.

#include <iostream>#include<cstdio>#include<cmath>#include<cstring>#include<cstdlib>#include<algorithm>#include<vector>#include<queue>UsingNamespace std;#defineINF 0X7FFFFFF#defineMAXN 510typedef longlong LL;#defineMin (A, B) (A&LT;B?A:B)#defineMOD 1000000007intm, N, Time, top, ans;intSTACK[MAXN], DFN[MAXN], LOW[MAXN], BLOCKS[MAXN];BOOLInstack[maxn];typedefstructnode{intE, W; Node (intE=0,intw=0): E (E), W (w) {}}node;vector<vector<node> >G;vector<vector<node> >G2;voidinit () {memset (DFN,0,sizeof(DFN)); memset (Low,0,sizeof(low)); Ans= time = top =0;    G.clear (); G.resize (n+2);    G2.clear (); G2.resize (n+2);}voidSPFA () {}voidTarjan (intu) {Low[u]= Dfn[u] = + +Time ; Stack[top++] =u; Instack[u]=true; intLen =g[u].size ();    Node V;  for(intI=0; i<len; i++) {v=G[u][i]; if( !LOW[V.E])            {Tarjan (V.E); Low[u]=min (Low[u], low[v.e]); } elseif (INSTACK[V.E]) Low[u]=min (Low[u], dfn[v.e]); }    intK; if(Dfn[u] = =Low[u]) {         Do{k= stack[--top]; INSTACK[K]=false; BLOCKS[K]=ans; } while(U! =k); Ans++; }}intSPFA (intStar,intEnd) {    intDIST[MAXN]; BOOLVIS[MAXN]; memset (Vis,false,sizeof(VIS));  for(intI=0; i<ans; i++) Dist[i]=INF; Dist[star]=0; Queue<node>Q;    Node P, Pn; Q.push (Node (Star,0) );  while(Q.size ()) {P=Q.front ();        Q.pop (); VIS[P.E]=true; intLen =g2[p.e].size ();  for(intI=0; i<len; i++) {Pn=G2[p.e][i]; if(DIST[PN.E] > DIST[P.E] +PN.W) {DIST[PN.E]= DIST[P.E] +PN.W; if(!VIS[PN.E])            Q.push (PN.E); }        }    }   //for (int i=0; i<ans; i++)//printf ("----%d\n", dist[i]); return dist[end];}voidsolve () {intK, A, B;  for(intI=1; i<=n; i++)    {        if(!Low[i])    Tarjan (i); }     for(intI=1; I <= N; i++)    {        intLen =g[i].size ();        Node V;  for(intj=0; j<len; J + +) {v=G[i][j]; A= Blocks[i], B =BLOCKS[V.E]; if(A! =b) {G2[a].push_back (node (B,V.W)); //printf ("%d->%d,%d\n", A, b, V.W); }}} scanf ("%d",&k);  while(K--) {scanf ("%d%d", &a, &b); A= Blocks[a], B =Blocks[b]; intrel =SPFA (A, b); if(rel = =INF) puts ("Nao e possivel entregar a carta"); Elseprintf ("%d\n", rel); } printf ("\ n");}intMain () { while(SCANF ("%d%d", &n, &m), m+N) {init ();  while(m--)        {            intA, B, C; scanf (" %d%d%d", &a, &b, &c);        G[a].push_back (Node (b,c));    } solve (); } Return0;}

POJ countries in War 3114