差分约束Poj 3169 Layout

#include <cstdio>
#include <cstdlib>
#include <cstring>
#include <algorithm>
#include <cmath>
#include <stack>
#include <queue>
#include <vector>
#include <map>
#include <string>
#include <iostream>
using namespace std;
int n;
const int INF=0xfffffff;
struct edge
{
	int val;int to;int next;
}e[111111];

int len;int head[11111];

void add(int from,int to,int val)
{
	e[len].to=to;e[len].val=val;e[len].next=head[from];head[from]=len++;
}
int dis[11111];
int spfa(int x)
{
	int vis[11111];
	for(int i=1;i<=n;i++) vis[i]=0;
	for(int i=1;i<=n;i++) dis[i]=INF;
	vis[x]=1; dis[x]=0;
	queue<int> q;
	q.push(x);  int cnt[11111]={0}; cnt[x]=1;
	while(!q.empty()){
		int cur=q.front(); q.pop();vis[cur]=0;
		for(int i=head[cur];i!=-1;i=e[i].next){
			int cc=e[i].to;
			if(dis[cc]>dis[cur]+e[i].val){
				dis[cc]=dis[cur]+e[i].val;
				if(!vis[cc]){
					cnt[cc]++;if(cnt[cc]>n) return 0;
					q.push(cc); vis[cc]=1;
				}
			}
		}
	}
	return 1;
}

int main()
{
	int m,l;
	while(scanf("%d%d%d",&n,&m,&l)!=EOF){
		len=0;memset(head,-1,sizeof(head));
		for(int i= 0;i<m;i++){
			int a,b,c;scanf("%d%d%d",&a,&b,&c);
			if(a>b) {int t=a;a=b;b=t;}
			add(a,b,c);
		}
		for(int i=0;i<l;i++){
			int a,b,c;scanf("%d%d%d",&a,&b,&c);
			if(a<b){int t=a;a=b;b=t;};
			add(a,b,-c);
		}
		if(!spfa(1)) printf("-1\n");
		else{
			if(dis[n]==INF)
				printf("-2\n");
			else
				printf("%d\n",dis[n]);
		}
	}
	return 0;
}