网络流24题之T10 餐巾计划问题

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这题。。写完了错了，找了快半小时，发现是inq和q搞差了，还有丢了一个p数组。。

#include <cstdio>#include <iostream>#include <cstdlib>#include <algorithm>#include <cstring>using namespace std ;const int oo=1000000000;const int maxn=2010;typedef struct EDGE{    int front,next;    int cap,flow;    int cost;}E;E edge[25010];int len=-1;struct READIN {    int p,f,n,m,s;}R;int n,s,t,tot;int head[maxn],next[25010];int q[maxn],inq[maxn];int dist[maxn],p[maxn],a[maxn];int S,T,allp;void E_add (int s,int t,int c,int f){    edge[++len].front=s;    edge[len].next=t;    edge[len].cap=c;    edge[len].cost=f;    next[len]=head[s];    head[s]=len;    edge[++len].front=t;    edge[len].next=s;    edge[len].cost=-f;    next[len]=head[t];    head[t]=len;}void init (){    freopen ("prog810.in","r",stdin);    freopen ("prog810.out","w",stdout);    scanf ("%d %d %d %d %d %d",&n,&R.p,&R.m,&R.f,&R.n,&R.s);    memset (head,-1,sizeof(head));    S=0;    T=2*n+1;    allp=T;    int i,j;    for (i=1;i<=n;i++){        scanf ("%d",&j);        E_add (S,i,j,0);        E_add (i+n,T,j,0);        E_add (S,i+n,oo,R.p);        if (i+1<=n) E_add (i,i+1,oo,0);        if (i+R.m<=n) E_add (i,i+n+R.m,oo,R.f);        if (i+R.n<=n) E_add (i,i+n+R.n,oo,R.s);    }}bool spfa (int &flow,int &cost){    int heads=0,tail=0;    int now,i;    for (i=0;i<=allp;i++) dist[i]=oo;    memset (inq,0,sizeof(inq));    dist[S]=0; inq[S]=1;p[S]=0;a[S]=oo;    q[tail++]=S;    while (heads!=tail){        now=q[heads++];        if (heads==2000) heads=0;        inq[now]=0;        for (i=head[now];i>=0;i=next[i]){            E &e=edge[i];            if (e.cap>e.flow&&dist[e.next]>dist[now]+e.cost){                dist[e.next]=dist[now]+e.cost;                p[e.next]=i;                a[e.next]=min (a[now],e.cap-e.flow);                if (!inq[e.next]){                    q[tail++]=e.next;                    if (tail==2000) tail=0;                    inq[e.next]=1;                }            }        }    }    if (dist[T]==oo) return false;    flow+=a[T];    cost+=dist[T]*a[T];    now=T;    while (now!=S){        edge[p[now]].flow+=a[T];        edge[p[now]^1].flow-=a[T];        now=edge[p[now]].front;    }    return true;}void work (){    int flow=0,cost=0;    while (spfa (flow,cost));    printf ("%d\n",cost);}int main (){    init ();    work ();    return 0;}

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