POJ 3169 SPFA difference constraint maximum value-> Shortest Path Method

This question is still normal ~ Saying ~ Still, the shortest path calculates the maximum value ....

The new question is that there are three situations.

1. No negative ring Solution

2. The distance is too far to reach N points not updated

3. Maximum Value

#include<iostream>#include<queue>#define MAXN 2005#define MAXM 20010#define INF 0x7F7F7F7Fusing namespace std;struct Node{       int v,price;       Node *next;}Edge[MAXM],*ptr[MAXN];int N,ML,MD;int edgeNum;void addEdge( int u,int v,int w ){     Node *p=&Edge[edgeNum++];     p->v=v;     p->price=w;     p->next=ptr[u];     ptr[u]=p;}int dist[MAXN];int minV,maxV;bool spfa(){     queue<int>myQueue;     int cnt[MAXN];     int used[MAXN];     memset( used,0,sizeof(used) );     memset( cnt,0,sizeof(cnt) );     memset( dist,0x7F,sizeof(dist) );     dist[minV]=0;     myQueue.push(minV);     while( !myQueue.empty() )     {            int u=myQueue.front();            myQueue.pop();            Node *p=ptr[u];            used[u]=false;            while( p )            {                   if( dist[p->v]>dist[u]+p->price )                   {                       dist[p->v]=dist[u]+p->price;                       if( !used[p->v] )                       {                           used[p->v]=true;                           myQueue.push(p->v);                           if( ++cnt[p->v]>N )                               return false;                       }                   }                   p=p->next;            }     }     return true;}int main(){    while( scanf( "%d %d %d",&N,&ML,&MD )!=EOF )    {           int i;           int u,v,w;           for( i=0;i<=N;i++ )                ptr[i]=NULL;           edgeNum=0;           maxV=0,minV=INF;           for( i=1;i<=ML;i++ )           {                scanf( "%d %d %d",&u,&v,&w );                if( u<minV )minV=u;                if( v>maxV )maxV=v;                addEdge( u,v,w );           }           for( i=1;i<=MD;i++ )           {                scanf( "%d %d %d",&u,&v,&w );                if( u<minV )minV=u;                if( v>maxV )maxV=v;                addEdge( v,u,-w );           }           if( !spfa() )               printf( "-1\n" );           else if( dist[maxV]==INF )                printf( "-2\n" );           else               printf( "%d\n",dist[maxV] );    }    return 0;}