poj 2983 Is the Information Reliable?

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


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

Edge edge[300000];     // 保存边的值
int  dist[1010];     // 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  引入附加源点V0
    
    for(int i=1; i<=nodenum; ++i)
        dist[i] = 99999999;
    dist[0] = 0;
    char ch;
    int a,b,x,i=0;
    while(e--)
    {
        scanf(" %c",&ch);
        if(ch=='P')        //P a,b,x a-b=x 可化为两个不等式：a-b>=x, a-b<=x
        {
            scanf("%d %d %d",&a,&b,&x);        //cin会TLE
            edge[++i].u=a;edge[i].v=b;edge[i].weight=-x;
            edge[++i].u=b;edge[i].v=a;edge[i].weight=x;
        }
        else
        {
            scanf("%d %d",&a,&b);
            edge[++i].u=a;edge[i].v=b;edge[i].weight=-1;
        }
    }
    edgenum=i;
}

// 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()
{
    while(cin >> nodenum >> e )
    {
        init();
        if(Bellman_Ford())
            printf("Reliable\n");
        else
            printf("Unreliable\n");
    }
    return 0;
}