HDU 1269 Maze Castle (DFS)

Maze Castle Problem description in order to train the sense of direction, Gardon built a large castle with N rooms (n<=10000) and M-Lanes (m<=100000), each one unidirectional, That is, if a channel is said to be connected to room A and room B, only the room B can be reached by this passage, but it does not mean that it can be reached by Room B. Gardon need to ask you to write a procedure to confirm whether any two rooms are interconnected, namely: for arbitrary I and J, there is at least one path can be from room I to room J, there is a path can be from room J to room I.

The input input contains more than one set of data, the first line of inputs has two numbers: N and M, and the next m row has two numbers a and B, indicating that a passage can come from room A to room B. The file ends with two 0. Output for each set of data entered, if any two rooms are connected to each other, outputs "Yes", otherwise output "No". Sample INPUT3 3
1 2
2 3
3 1
7 ·
1 2
2 3
3 2
0 0 Sample Outputyes
No answer violence DFS, starting from the first room search: 1->2->3, because of the existence of the ring, to determine whether to return to the starting point, otherwise it will be infinite loop. A room can go to a room with set to record, not repeat.

#include <Set>#include<cmath>#include<queue>#include<vector>#include<cstdio>#include<string>#include<cstring>#include<iostream>#include<algorithm>#defineMS (a) memset (A,0,sizeof (a))#defineMSP Memset (Mp,0,sizeof (MP))#defineMSV memset (vis,0,sizeof (VIS))using namespacestd;intn,m;BOOLvis[10001];Set<int> s[10001];voidDfsintOriintx) {    Set<int>:: Iterator it; Vector<int>v;  for(It=s[x].begin (); It!=s[x].end (); it++) V.push_back (*it); Vector<int>:: iterator ITV;  for(Itv=v.begin (); Itv!=v.end (); itv++)    {        if(Vis[*itv])Continue; //If the room you are searching for is smaller than the starting room number, it means that the room has been searched.//at this point, just insert all the rooms that you can walk into .        /*//This pruning has a problem if (*itv<ori) {for (It=s[*itv].begin (); It!=s[*itv].end (); it++) {                if (*it==ori) continue;            S[ori].insert (*it);        } continue; }        */S[ori].insert (*ITV); vis[*itv]=1; DFS (Ori,*ITV); }}intMain () { while(cin>>n>>m&& (n| |m)) { while(m--)        {            intb; CIN>>a>>b;        S[a].insert (b); }        BOOLflag=1;  for(intI=1; i<=n; i++)        {            if((int) s[i].size () ==n-1)Continue;            msv Vis[i]=1;            DFS (i,i); //pruning, if a room cannot walk to all the other rooms,//There's no further search .            if((int) s[i].size ()!=n-1) {flag=0;  Break; }        }         for(intI=1; i<=n&&flag;i++)        {            if((int) s[i].size ()!=n-1) {flag=0; }        }        if(flag) printf ("yes\n"); Elseprintf"no\n");  for(intI=1; i<=n;i++) s[i].clear (); }    return 0;}

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HDU 1269 Maze Castle (DFS)