BZOJ3280: 小R的烦恼

#include<cmath>
#include<cstdio>
#include<cstdlib>
#include<cstring>
#include<algorithm>
using namespace std;
struct node{
    int x,y,c,d,next,other;
}a[2100000];int len,last[2100000];
const int INF=99999999;
void ins(int x,int y,int c,int d)
{
    int k1,k2;
    k1=++len;
    a[len].x=x;a[len].y=y;a[len].c=c;a[len].d=d;
    a[len].next=last[x];last[x]=len;
    
    k2=++len;
    a[len].x=y;a[len].y=x;a[len].c=0;a[len].d=-d;
    a[len].next=last[y];last[y]=len;
    
    a[k1].other=k2;
    a[k2].other=k1;
}
int st,ed;
int head,tail,list[21000];
int pre[21000],cc[21000],d[21000];
bool v[21000];
int ans,flow;
bool spfa()
{
    for(int i=1;i<=ed;i++)d[i]=999999999;
    d[st]=0;
    memset(cc,0,sizeof(cc));cc[st]=9999999;
    memset(v,false,sizeof(v));v[st]=true;
    list[1]=st;head=1;tail=2;
    while(head<=tail)
    {
        int x=list[head];
        for(int k=last[x];k;k=a[k].next)
        {
            int y=a[k].y;
            if(d[y]>d[x]+a[k].d&&a[k].c>0)
            {
                d[y]=d[x]+a[k].d;
                cc[y]=min(cc[x],a[k].c);
                pre[y]=k;
                if(v[y]==false)
                {
                    v[y]=true;
                    list[tail++]=y;
                    if(tail==20000)tail=1;
                }
            }
        }
        v[x]=false;
        head++;if(head==20000)head=1;
    }
    if(d[ed]==999999999)return false;
    ans+=cc[ed]*d[ed];flow+=cc[ed];
    int x=ed;
    while(x!=0)
    {
        int k=pre[x];
        a[k].c-=cc[ed],a[a[k].other].c+=cc[ed];
        x=a[k].x;
    }
    return true;
}
int main()
{
    int T;
    scanf("%d",&T);
    for(int ti=1;ti<=T;ti++)
    {
        int n,m,k;
        len=0;memset(last,0,sizeof(last));
        scanf("%d%d%d",&n,&m,&k);
        st=0,ed=2*n+m+1;
        int sum=0;flow=ans=0;
        for(int i=1;i<=n;i++)
        {
            int x;
            scanf("%d",&x);sum+=x;
            ins(st,i,x,0);ins(i+n,ed,x,0);
            if(i!=n)ins(i,i+1,INF,0);
        }
        for(int i=1;i<=m;i++)
        {
            int x,y;
            scanf("%d%d",&x,&y);
            ins(st,i+2*n,x,0);
            for(int j=1;j<=n;j++)ins(i+2*n,j+n,x,y);
        }
        for(int i=1;i<=k;i++)
        {
            int x,y;
            scanf("%d%d",&x,&y);
            for(int j=1;j<=n;j++)
                if(j+x+1<=n)
                    ins(j,j+x+1+n,INF,y);
        }
        while(spfa()==true){}
        printf("Case %d: ",ti);
        if(flow==sum)printf("%d\n",ans);
        else printf("impossible\n");
    }
    return 0;
}