最大流(邻接表实现)

这是来自zjut-vegetable的好东西~~收藏下,邻接表是个好东西!

 

#include<iostream>
using namespace std;
const int maxn=205;
const int inf=1000000000;
int pre[maxn],que[maxn],d[maxn],v[maxn];
struct node
{
    int v,val,next;
}s[505];
int flow[505];
int p[205];
int ind;
int id[505];
int maxflow(int source,int sink)
{
    int h,r,ret=0,i,j,k;
    memset(flow,0,sizeof(flow));
    for(;;)
    {
        memset(v,0,sizeof(v));
        memset(d,0,sizeof(d));
        que[0]=source;
        v[source]=1;
        d[source]=inf;
        h=r=0;
        while(h<=r &&!v[sink])
        {
            k=que[h++];
            for(int q=p[k];q!=-1;q=s[q].next)
            {
                i=s[q].v;
                if(!v[i]&&flow[q]<s[q].val)
                {
                    v[i]=1;
                    que[++r]=i;
                    pre[i]=k;
                    id[i]=q;
                    d[i]=min(s[q].val-flow[q],d[k]);
                }
            }
        }
        if(!v[sink])break;
        ret+=d[sink];
        for(i=sink;i!=source;)
        {
            j=i;
            i=pre[i];
            flow[id[j]]+=d[sink];
            k=id[j];
            if(k<ind)
                k+=ind;
            else
                k-=ind;
            flow[k]=-flow[id[j]];
        }
    }
    return ret;
}
int main()
{
    int m,n;
    while(cin>>m>>n)
    {
        int x,y,z;
        memset(p,-1,sizeof(p));
        ind=m;
        for(int i=0;i<m;i++)
        {
            cin>>x>>y>>z;
            s[i].v=y;
            s[i].next=p[x];
            s[i].val=z;
            p[x]=i;
            s[i+m].v=x;
            s[i+m].next=p[y];
            s[i+m].val=0;
            p[y]=i+m;
        }
        cout<<maxflow(1,n)<<endl;
    }
}