BZOJ 2330 [SCOI2011]糖果 差分约束系统

#include <cstdio>
#include <cstring>
#include <queue>
#define N 100005
using namespace std;
struct Edge {
    int from,to,nxt,val;
    Edge() {}
    Edge(int _from,int _to,int _nxt,int _val):
        from(_from),to(_to),nxt(_nxt),val(_val) {}
}e[N*5];
int n,m,tot,fir[N],d[N];
void Add_Edge(int from,int to,int val) {
    e[++tot]=Edge(from,to,fir[from],val), fir[from]=tot;
    return ;
}
bool SPFA() {
    static int cnt[N];
    static bool inq[N];
    queue<int> q;
    q.push(0), inq[0]=true;
    while(!q.empty()) {
        int x=q.front(); q.pop();
        inq[x]=false;
        for(int i=fir[x];~i;i=e[i].nxt) {
            if(d[e[i].to]>=d[x]+e[i].val) continue;
            d[e[i].to]=d[x]+e[i].val;
            cnt[e[i].to]=cnt[x]+1;
            if(cnt[e[i].to]>n+1) return false;
            if(!inq[e[i].to]) q.push(e[i].to), inq[e[i].to]=true;
        }
    }
    return true;
}
int main() {
    memset(fir,-1,sizeof fir), tot=-1;
    scanf("%d%d",&n,&m);
    for(int i=n;i;--i) Add_Edge(0,i,1);
    for(int i=1,mode,x,y;i<=m;++i) {
        scanf("%d%d%d",&mode,&x,&y);
        if(mode==1) Add_Edge(x,y,0), Add_Edge(y,x,0);
        if(mode==2) Add_Edge(x,y,1);
        if(mode==3) Add_Edge(y,x,0);
        if(mode==4) Add_Edge(y,x,1);
        if(mode==5) Add_Edge(x,y,0);
    }
    if(!SPFA()) {
        puts("-1");
        return 0;
    }
    long long ans=0;
    for(int i=1;i<=n;++i) ans+=d[i];
    printf("%lld\n",ans);
    return 0;
}