poj 3169 Layout

#include <iostream>                //差分约束系统，Bellman-Ford算法
using namespace std;
const int inf=99999999;

typedef struct Edge{
    int u, v;    // 起点，重点
    int weight;  // 边的权值
}Edge;

Edge edge[20020];     // 保存边的值
int  dist[1005];     // 结点到源点最小距离

int nodenum, e,edgenum;    // 结点数，边数，源点

// 初始化图
void init()
{
    // 输入结点数，边数  源点为V1
    int ml,md;
    cin>>nodenum>>ml>>md;
    edgenum=ml+md;
    for(int i=2; i<=nodenum; ++i)
        dist[i] = inf;
    dist[1] = 0;
    int a,b,d,i=0;
    while(ml--)
    {
        cin>>a>>b>>d;
        edge[++i].u=a;edge[i].v=b;edge[i].weight=d;
    }
    while(md--)
    {
        cin>>a>>b>>d;
        edge[++i].u=b;edge[i].v=a;edge[i].weight=-d;
    }
}

// 松弛计算
bool relax(int u, int v, int weight)
{
    if(dist[v] > dist[u] + weight)
    {
        dist[v] = dist[u] + weight;
        return 1;
    }
    return 0;
}

bool Bellman_Ford()
{
    for(int i=1; i<=nodenum-1; ++i)
    {
        int tag=1;
        for(int j=1; j<=edgenum; ++j)
        {
            if(!relax(edge[j].u, edge[j].v, edge[j].weight))
                tag=0;
        }
        if(tag)
            break;
    }

    // 判断是否有负环路
    for(int i=1; i<=edgenum; ++i)
        if(dist[edge[i].v] > dist[edge[i].u] + edge[i].weight)
            return 0;
    return 1;
}
int main()
{
        init();
        if(!Bellman_Ford())
            cout<<"-1\n";
        else if(dist[nodenum]==inf)
            cout<<"-2\n";
        else
            cout<<dist[nodenum]<<endl;
    
    return 0;
}