【费用流】bzoj1520 [POI2006]Szk-Schools

注意：建图的时候，一定要把旧标号相同的分开。

#include<cstdio>
#include<algorithm>
#include<cstring>
#include<queue>
using namespace std;
#define MAXN 5001
#define MAXM 100001
#define INF 2147483647
int S,T,n,x,A,B,C;
int en,u[MAXM],v[MAXM],first[MAXN],next[MAXM],cap[MAXM],cost[MAXM];//Next Array
bool inq[MAXN];
int d[MAXN]/*spfa*/,p[MAXN]/*spfa*/,a[MAXN]/*可改进量*/;
queue<int>q;
void Init_MCMF(){memset(first,-1,sizeof(first));en=0;S=0;T=(n<<1|1);}
void AddEdge(const int &U,const int &V,const int &W,const int &C)
{
    u[en]=U; v[en]=V; cap[en]=W; cost[en]=C;
    next[en]=first[U]; first[U]=en++;
    u[en]=V; v[en]=U; cost[en]=-C;
    next[en]=first[V]; first[V]=en++;
}
bool Spfa(int &Flow,int &Cost)
{
    memset(d,0x7f,sizeof(d));
    memset(inq,0,sizeof(inq));
    d[S]=0; inq[S]=1; p[S]=0; a[S]=INF; q.push(S);
    while(!q.empty())
      {
        int U=q.front(); q.pop(); inq[U]=0;
        for(int i=first[U];i!=-1;i=next[i])
          if(cap[i] && d[v[i]]>d[U]+cost[i])
            {
              d[v[i]]=d[U]+cost[i];
              p[v[i]]=i;
              a[v[i]]=min(a[U],cap[i]);
              if(!inq[v[i]]) {q.push(v[i]); inq[v[i]]=1;}
            }
      }
    if(d[T]>2000000000) return 0;
    Flow+=a[T]; Cost+=d[T]*a[T]; int U=T;
    while(U!=S)
      {
        cap[p[U]]-=a[T]; cap[p[U]^1]+=a[T];
        U=u[p[U]];
      }
    return 1;
}
void Mincost()
{
    int Flow=0,Cost=0;
    while(Spfa(Flow,Cost));
    if(Flow==n) printf("%d\n",Cost);
    else puts("NIE");
}
int Abs(const int &v){return v<0 ? -v : v;}
int main()
{
    scanf("%d",&n); Init_MCMF();
    for(int j=1;j<=n;++j)
      {
          scanf("%d%d%d%d",&x,&A,&B,&C);
          AddEdge(S,j,1,0);
          for(int i=A;i<=B;++i) AddEdge(j,i+n,1,Abs(i-x)*C);
      }
    for(int i=1;i<=n;++i) AddEdge(i+n,T,1,0);
    Mincost();
    return 0;
}