FZU-1924+判断环/DFS/BFS

dfs：

/*

*/
#include<stdio.h>
#include<string.h>
#include<stdlib.h>
#include<algorithm>
#include<iostream>
#include<queue>
#include<map>
#include<stack>
#include<set>
#include<math.h>
using namespace std;
typedef long long int64;
//typedef __int64 int64;
typedef pair<int64,int64> PII;
#define MP(a,b) make_pair((a),(b)) 
const int maxn = 1005;
const int inf = 0x7fffffff;
const double pi=acos(-1.0);
const double eps = 1e-8;

int vis[ maxn ];
struct Edge{
	int u,next;
}edge[ maxn<<4 ];
int cnt,head[ maxn ];
void init(){
	memset( vis,-1,sizeof( vis ) );
	cnt = 0;
	memset( head,-1,sizeof( head ) );
}
void addedge( int a,int b ){
	edge[ cnt ].u = b;
	edge[ cnt ].next = head[ a ];
	head[ a ] = cnt++;
}

bool flag;
int ans;
void dfs( int cur ){
	if( flag ) return ;
	vis[ cur ] = 1;
	for( int i=head[ cur ];i!=-1;i=edge[i].next ){
		int nxt = edge[i].u;
		if(nxt == ans){
			flag = true;
			return;
		}
		if(vis[ nxt ] == 1)continue;
		if( flag )return;
		dfs( nxt );	
	}
}
			

int main(){
	int T;
	scanf("%d",&T);
	int Case = 1;
	while( T-- ){
		int n,m;
		scanf("%d%d",&n,&m);
		int edge_a,edge_b;
		scanf("%d%d",&edge_a,&edge_b);
		int x,y;
		init();
		while( edge_a-- ){
			scanf("%d%d",&x,&y);
			x++,y++;
			y += n;
			addedge( x,y );
		}
		while( edge_b-- ){
			scanf("%d%d",&x,&y);
			x++,y++;
			x += n;
			addedge( x,y );
		}
		flag = false;

		for( int i=1;i<=n;i++ ){
			memset(vis,0,sizeof(vis));
			ans = i;
			dfs(i);
			if(flag)break;
			/*
			if( flag==false&&vis[i]==-1 ){
				dfs( i,-1 );
			}
			*/
		}		
		printf("Case %d: ",Case ++ );
		if( flag ) printf("Possible\n");
		else printf("Impossible\n");
	}
	return 0;
}

bfs：

/*

*/
#include<stdio.h>
#include<string.h>
#include<stdlib.h>
#include<algorithm>
#include<iostream>
#include<queue>
#include<map>
#include<stack>
#include<set>
#include<math.h>
using namespace std;
typedef long long int64;
//typedef __int64 int64;
typedef pair<int64,int64> PII;
#define MP(a,b) make_pair((a),(b)) 
const int maxn = 1005;
const int inf = 0x7fffffff;
const double pi=acos(-1.0);
const double eps = 1e-8;

int vis[ maxn ];
struct Edge{
	int u,next;
}edge[ maxn<<4 ];
int cnt,head[ maxn ];
void init(){
	//memset( vis,-1,sizeof( vis ) );
	cnt = 0;
	memset( head,-1,sizeof( head ) );
}
void addedge( int a,int b ){
	edge[ cnt ].u = b;
	edge[ cnt ].next = head[ a ];
	head[ a ] = cnt++;
}

bool flag;

void dfs( int cur,int fa ){
	if( flag ) return ;
	vis[ cur ] = 1;
	for( int i=head[ cur ];i!=-1;i=edge[i].next ){
		int nxt = edge[i].u;
		if( fa==-1 ){
			dfs( nxt,cur );
		}
		else {
			if( nxt==fa ) continue;
			else {
				if( vis[nxt]==1 ){
					flag = true;
					return ;
				}
				else {
					dfs( nxt,cur );
				}
			}
		}
	}
}

void bfs( int s ){
	memset( vis,0,sizeof( vis ) );
	queue<int>q;
	vis[ s ] = 1;
	q.push( s );
	while( !q.empty() ){
		int cur = q.front();
		q.pop();
		for( int i=head[cur];i!=-1;i=edge[i].next ){
			int nxt = edge[i].u;
			vis[ nxt ] ++;
			if( vis[nxt]==1 ){
				q.push( nxt );
			}
			else {flag = true;return;}
		}
	}
}


int main(){
	int T;
	scanf("%d",&T);
	int Case = 1;
	while( T-- ){
		int n,m;
		scanf("%d%d",&n,&m);
		int edge_a,edge_b;
		scanf("%d%d",&edge_a,&edge_b);
		int x,y;
		init();
		while( edge_a-- ){
			scanf("%d%d",&x,&y);
			x++,y++;
			y += n;
			addedge( x,y );
		}
		while( edge_b-- ){
			scanf("%d%d",&x,&y);
			x++,y++;
			x += n;
			addedge( x,y );
		}
		flag = false;
		//for( int i=1;i<=n;i++ ){
		//	if( flag==false&&vis[i]==-1 ){
		//		dfs( i,-1 );
		//	}
		//}
		for( int i=1;i<=n;i++ ){
			if( flag==false )
				bfs( i );
		}		
		printf("Case %d: ",Case ++ );
		if( flag ) printf("Possible\n");
		else printf("Impossible\n");
	}
	return 0;
}