POJ 3169 Layout

查分约束好题，关键在于转化！

#include<iostream>
using namespace std;
#define MAX 20020
#define INF 999999
struct Node{
    int u,v;
    int val;
}node[MAX];
int nv,ne,start;
int dist[MAX];
int bellman_DC()
{
    int i,j,tmp,tag;
    for(i=1;i<=nv;++i)
        dist[i] = INF;
    dist[start] = 0;
    for(i=1;i<nv;++i)
    {
        tag = 0;
        for(j=1;j<=ne;++j)
        {
            tmp = dist[node[j].u]+node[j].val;
            if(tmp<dist[node[j].v])
            {
                dist[node[j].v] = tmp;
                tag = 1;
            }
        }
        if(tag == 0)
            return 0;
    }
    for(i=1;i<=ne;++i)
        if(dist[node[i].v]>dist[node[i].u]+node[i].val)
            return 1;
    return 0;
}
int main()
{
    int i,j,a,b,flag,m1,m2,val,index;
    while(scanf("%d%d%d",&nv,&m1,&m2)!=EOF)
    {
        index = 0;
        ne = m1+m2;
        for(i=1;i<=m1;++i)
        {
            ++index;
            scanf("%d%d%d",&a,&b,&val);
            node[index].u = a;
            node[index].v = b;
            node[index].val = val;
        }
        for(i=1;i<=m2;++i)
        {
            ++index;
            scanf("%d%d%d",&a,&b,&val);
            node[index].u = b;
            node[index].v = a;
            node[index].val = -val;
        }
        start = 1;
        flag = bellman_DC();
        if(flag == 1)
            printf("-1\n");
        else if(dist[nv]==INF)
            printf("-2\n");
        else 
            printf("%d\n",dist[nv]);
    }
    return 0;
}