hihocode#1378 : 网络流二·最大流最小割定理(最大流求最小割集)

题目链接

EK求最小割集模板

代码：

#include<cstdio>#include<cstring>#include<algorithm>#include<iostream>#include<string>#include<vector>#include<stack>#include<bitset>#include<cstdlib>#include<cmath>#include<set>#include<list>#include<deque>#include<map>#include<queue>using namespace std;typedef long long ll;const double PI = acos(-1.0);const double eps = 1e-6;const int INF = 1000000000;const int maxn = 123456;int T,n,m;int tot,s,t;int head[maxn],vis[maxn],path[maxn];set<int>st;struct EDGE{    int from,to;    int cap,flow;    int next;}e[maxn];void init(){    tot=0;    s=1;    t=n;    memset(head,-1,sizeof(head));    memset(vis,0,sizeof(vis));    memset(path,0,sizeof(path));}void add_edge(int u,int v,int w){    e[tot].from=u;    e[tot].to=v;    e[tot].cap=w;    e[tot].flow=0;    e[tot].next=head[u];    head[u]=tot++;}int bfs(){    queue<int>q;    q.push(s);    vis[s]=1;    path[s]=-1;    while(!q.empty())    {        int u=q.front();        q.pop();        for(int i=head[u];i!=-1;i=e[i].next)        {            int v=e[i].to;            if(e[i].cap-e[i].flow>0&&!vis[v])            {                path[v]=i;                vis[v]=1;                if(v==t)                    return 1;                q.push(v);            }        }    }    return 0;}int EK(){    int maxFlow=0;    int flow,i;    while(bfs())    {        memset(vis,0,sizeof(vis));        i=path[t];        flow=INF;        while(i!=-1)        {            flow=min(flow,e[i].cap-e[i].flow);            i=path[e[i].from];        }        i=path[t];        while(i!=-1)        {            e[i].flow+=flow;            e[i^1].flow-=flow;            i=path[e[i].from];        }        maxFlow+=flow;    }    return maxFlow;}void Get_set()//求割集{    memset(vis,0,sizeof(vis));    queue<int>q;    q.push(1);    vis[1]=1;    while(!q.empty())    {        int u=q.front();        q.pop();        st.insert(u);        for(int i=head[u];i!=-1;i=e[i].next)        {            int v=e[i].to;            if(vis[v]==0&&e[i].cap-e[i].flow>0)            {                vis[v]=1;                q.push(v);            }        }    }}int main(){    while(scanf("%d%d",&n,&m)!=EOF)    {        init();        for(int i=0;i<m;i++)        {            int u,v,c;            scanf("%d%d%d",&u,&v,&c);            add_edge(u,v,c);            add_edge(v,u,0);        }        int maxFlow=EK();        Get_set();        printf("%d %d\n",maxFlow,st.size());        for(set<int>::iterator it = st.begin();it!=st.end();it++)        {            if(it!=st.begin())                printf(" ");            printf("%d",*it);        }        printf("\n");    }    return 0;}