HDU1224 SPFA

题意：给定一张图，求从1到n+1的最长距离。

bfs即可，没什么技巧。

#include<stdio.h>
#include<string.h>
#include<stdlib.h>
#include<algorithm>
#include<queue>
#include<stack>
using namespace std;
const int maxn = 105;
const int maxm = 10000;
const int inf = 99999999;
int cnt,head[ maxn ];
struct node{
    int u,val,next;
}edge[ maxm ];
int n,m;
int val[ maxn ];
int dis[  maxn ],vis[ maxn ],path[ maxn ];

void init(){
    cnt=0;
    memset( head,-1,sizeof( head ));
}

void addedge( int a,int b,int c ){
    edge[ cnt ].u=b;
    edge[ cnt ].val=c;
    edge[ cnt ].next=head[ a ];
    head[ a ]=cnt++;
}

void bfs(){
    for( int i=1;i<=n+1;i++ ){
        vis[i]=0;
        dis[i]=-inf;
        path[i]=-1;
    }
    queue<int>q;
    while( !q.empty() )
        q.pop();
    q.push( 1 );
    vis[1]=1;
    dis[1]=0;
    while( !q.empty() ){
        int now=q.front();
        q.pop();
        vis[ now ]=0;
        for( int i=head[ now ];i!=-1;i=edge[ i ].next ){
            int next=edge[i].u;
            if( dis[next]<dis[now]+val[next] ){
                dis[next]=dis[now]+val[next];
                path[next]=now;
                if( vis[next]==0 ){
                    vis[next]=1;
                    q.push(next);
                }
            }
        }
    }
}
void output(){
    printf("points : %d\n",dis[n+1]);
    stack<int>s;
    for( int i=n+1;i!=-1;i=path[i] ){
        s.push( i );
    }
    printf("circuit : ");
    printf("%d",s.top());
    s.pop();
    while( !s.empty() ){
        if( s.top()==(n+1) )
            printf("->%d",1);
        else
            printf("->%d",s.top());
        s.pop();
    }
    printf("\n");
}
int main(){
    int T;
    scanf("%d",&T);
    for( int ca=1;ca<=T;ca++ ){
        if( ca!=1 )
            printf("\n");
        scanf("%d",&n);
        for( int i=1;i<=n;i++ )
            scanf("%d",&val[ i ]);
        val[n+1]=0;
        scanf("%d",&m);
        int a,b;
        init();
        while( m-- ){
            scanf("%d%d",&a,&b);
            if( a<b ){
                addedge( a,b,0 );
            }
            else if( a>b ){
                addedge( b,a,0 );
            }
        }
        bfs();
        printf("CASE %d#\n",ca);
        //printf("%d\n",dis[n+1]);
        output();
    }
    return 0;
}