POJ 1459 Power Network

最大流-多源多匯問題

建立超級源點，超級匯點

#include<iostream>#include<cstring>#include<queue>#include<vector>using namespace std;const int inf=0xfffffff;queue<int>q;int n,np,nc,m,s,t;int cap[105][105],flow[105][105],d[105],g[105][105];int main(){    int i,a,b,c,f,ss;    char s1,s2,s3;    while(cin>>n>>np>>nc>>m)    {        s=n;t=n+1;        memset(cap,0,sizeof(cap));        memset(flow,0,sizeof(flow));        memset(g,0,sizeof(g));        for(i=0;i<m;i++)        {            cin>>s1>>a>>s2>>b>>s3>>c;            if(a==b) continue;            cap[a][b]=c;            g[a][++g[a][0]]=b;        }        for(i=0;i<np;i++)        {            cin>>s1>>a>>s2>>c;            cap[s][a]=c;            g[s][++g[s][0]]=a;        }        for(i=0;i<nc;i++)        {            cin>>s1>>a>>s2>>c;            cap[a][t]=c;            g[a][++g[a][0]]=t;        }        f=0;        int p[105];        for(;;)        {            memset(d,0,sizeof(d));            d[s]=inf;            q.push(s);ss=0;            while(!q.empty())            {                int u=q.front();q.pop();                for(int v=1;v<=g[u][0];v++) if(!d[g[u][v]] && cap[u][g[u][v]]>flow[u][g[u][v]])                {                    p[g[u][v]]=u;q.push(g[u][v]);                    int tt=cap[u][g[u][v]]-flow[u][g[u][v]];                    d[g[u][v]]=d[u]<tt?d[u]:tt;                    if(g[u][v]==t)                    {                        ss=1;break;                    }                }                if(ss) break;            }            while(!q.empty()) q.pop();            if(d[t]==0) break;            for(int u=t;u!=s;u=p[u])            {                flow[p[u]][u]+=d[t];                flow[u][p[u]]-=d[t];            }            f+=d[t];        }        cout<<f<<endl;    }    return 0;}