hdu2448 / 費用流 / harbin賽區c題

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題（自）目（己）錯（英）綜（語）複（太）雜（差），關係理了半小時+翻譯才看明白，看明白之後，直接建圖，費用流擊殺。/簡單題。

2A:有的地方，可用互連的要建雙向邊！

#include<cstdio>#include<iostream>#include<queue>#include<cstring>#include<string>using namespace std;const int maxv=400;const int maxe=400*400*2+800;const int inf=0x3f3f3f3f;int nume=0;int e[maxe][4];int head[maxv];int n,m,k,p;void inline adde(int i,int j,int c,int w){    e[nume][0]=j;e[nume][1]=head[i];head[i]=nume;    e[nume][2]=c;e[nume++][3]=w;    e[nume][0]=i;e[nume][1]=head[j];head[j]=nume;    e[nume][2]=0;e[nume++][3]=-w;}int inq[maxv];int pre[maxv];int prv[maxv];int d[maxv];int froms[maxv];bool spfa(int &sum,int &flow){    int s=0,t=n+m+1;    for(int i=0;i<=t;i++)          {              inq[i]=0;              d[i]=inf;          }    queue<int>q;    q.push(s);    inq[s]=1;    d[s]=0;    while(!q.empty())    {        int cur=q.front();        q.pop();        inq[cur]=0;        for(int i=head[cur];i!=-1;i=e[i][1])        {            int v=e[i][0];            if(e[i][2]>0&&d[cur]+e[i][3]<d[v])            {                d[v]=d[cur]+e[i][3];                pre[v]=i;                prv[v]=cur;                if(!inq[v])                {                    q.push(v);                    inq[v]=1;                }            }        }    }    if(d[t]==inf)return 0;    int cur=t;    int minf=inf;    while(cur!=s)    {        int fe=pre[cur];        minf=e[fe][2]<minf?e[fe][2]:minf;        cur=prv[cur];    }     cur=t;    while(cur!=s)    {        e[pre[cur]][2]-=minf;        e[pre[cur]^1][2]+=minf;        cur=prv[cur];    }    flow+=minf;    sum+=d[t]*minf;    return 1;}int mincost(int &flow){    int sum=0;   while(spfa(sum,flow));    return sum;}void init(){    nume=0;    for(int i=0;i<=n+m+5;i++)       head[i]=-1;}void read_build(){     for(int j=0;j<n;j++)          scanf("%d",&froms[j]);      int aa,bb,cc;     for(int i=0;i<k;i++)     {        scanf("%d%d%d",&aa,&bb,&cc);        adde(aa,bb,inf,cc);        adde(bb,aa,inf,cc);     }     for(int i=0;i<p;i++)     {        scanf("%d%d%d",&aa,&bb,&cc);        adde(bb,aa+m,inf,cc);      //   adde(aa+m,bb,inf,cc);     }      for(int i=0;i<n;i++)      {          adde(0,froms[i],1,0);          adde(m+1+i,n+m+1,1,0);      }    /* for(int i=0;i<=2*n+1;i++)       for(int j=head[i];j!=-1;j=e[j][1])       {           printf("%d->%d:f %dw %d\n",i,e[j][0],e[j][2],e[j][3]);       }*/}int main(){    while(~scanf("%d%d%d%d",&n,&m,&k,&p))    {        init();        read_build();        int flow=0;        int ans=mincost(flow);         printf("%d\n",ans);    }    return 0;}