bzoj2330: [SCOI2011]糖果（差分约束）

　　差分约束裸题，a==b的话分别建a>=b a<=b的边就行。倒序加边不然会TLE是什么鬼

#include<iostream>
#include<cstring>
#include<cstdlib>
#include<cstdio>
#define ll long long
using namespace std;
const int maxn=,inf=1e9;
struct poi{int too,pre,sum;}e[maxn];
int n,m,x,y,z,front,rear,tot;
ll dist[maxn],ans;
int h[maxn],v[maxn],last[maxn],tim[maxn];
bool flag;
void read(int &k)
{
    int f=;k=;char c=getchar();
    while(c<''||c>'')c=='-'&&(f=-),c=getchar();
    while(c<=''&&c>='')k=k*+c-'',c=getchar();
    k*=f;
}
void add(int x,int y,int z){e[++tot].too=y;e[tot].sum=z;e[tot].pre=last[x];last[x]=tot;}
void spfa()
{
    for(int i=;i<=n;i++)dist[i]=-inf;
    dist[]=;v[]=;front=rear=;h[++rear]=;
    while(front!=rear)
    {
        int now=h[++front];if(front==maxn)front=-;
        for(int i=last[now],too=e[i].too;i;i=e[i].pre,too=e[i].too)
        if(dist[too]<dist[now]+e[i].sum)
        {
            dist[too]=dist[now]+e[i].sum;
            if(++tim[too]>){printf("-1");flag=;return;}
            if(!v[too])
            {
                v[too]=;h[++rear]=too;
                if(rear==maxn)rear=-;
            }
        }
        v[now]=;
    }
}
int main()
{
    read(n);read(m);
    for(int i=n;i;i--)add(,i,);
    for(int i=;i<=m;i++)
    {
        read(z);read(x);read(y);
        if(z==)add(x,y,),add(y,x,);
        if(z==)
        {
            if(x==y){printf("-1");return ;}
            add(x,y,);
        }
        if(z==)add(y,x,);
        if(z==)
        {
            if(x==y){printf("-1");return ;}
            add(y,x,);
        }
        if(z==)add(x,y,);
    }
    spfa();
    if(flag)return ;
    for(int i=;i<=n;i++)ans+=dist[i];
    printf("%lld\n",ans);
    return ;
}