最大流ISAP模板

来源：互联网发布：数据分析表格怎么做编辑：程序博客网时间：2024/05/16 09:08
//复杂度O（n^2*m）一般比dinic快些
#include<bits/stdc++.h>using namespace std;struct Edge{    int from,to,cap,flow;};const int maxn=650;const int INF=0x3f3f3f3f;struct ISAP{    int n,m,s,t;//结点数，边数（包括反向弧），源点编号，汇点编号    vector<Edge>edges;    vector<int>G[maxn];    bool vis[maxn];    int d[maxn];    int cur[maxn];    int p[maxn];    int num[maxn];    void AddEdge(int from,int to,int cap){        edges.push_back((Edge){from,to,cap,0});        edges.push_back((Edge){to,from,0,0});        m=edges.size();        G[from].push_back(m-2);        G[to].push_back(m-1);    }    bool RevBFS(){        memset(vis,0,sizeof(vis));        queue<int>Q;        Q.push(t);        d[t]=0;        vis[t]=1;        while(!Q.empty()){            int x=Q.front();Q.pop();            for(int i=0;i<G[x].size();i++){                Edge &e =edges[G[x][i]^1];                if(!vis[e.from]&&e.cap>e.flow){                    vis[e.from]=1;                    d[e.from]=d[x]+1;                    Q.push(e.from);                }            }        }        return vis[s];    }    int Augment(){        int x=t, a=INF;        while(x!=s){            Edge &e = edges[p[x]];            a= min(a,e.cap-e.flow);            x=edges[p[x]].from;        }        x=t;        while(x!=s){            edges[p[x]].flow+=a;            edges[p[x]^1].flow-=a;            x=edges[p[x]].from;        }        return a;    }    int Maxflow(int s,int t,int n){        this->s=s,this->t=t,this->n=n;        int flow=0;        RevBFS();        memset(num,0,sizeof(num));        for(int i=0;i<n;i++){            num[d[i]]++;        }        int x=s;        memset(cur,0,sizeof(cur));        while(d[s]<n){            if(x==t){                flow+=Augment();                x=s;            }            int ok=0;            for(int i=cur[x];i<G[x].size();i++){                Edge &e =edges[G[x][i]];                if(e.cap>e.flow&&d[x]==d[e.to]+1){                    ok=1;                    p[e.to]=G[x][i];                    cur[x]=i;                    x=e.to;                    break;                }            }            if(!ok){                int m=n-1;                for(int i=0;i<G[x].size();i++){                    Edge &e =edges[G[x][i]];                    if(e.cap>e.flow)                        m=min(m,d[e.to]);                }                if(--num[d[x]]==0)                    break;                num[d[x]=m+1]++;                cur[x]=0;                if(x!=s)                    x=edges[p[x]].from;            }        }        return flow;    }};int main(){    int n,m,a,b,c,res;    while(scanf("%d%d",&m,&n)!=EOF){        ISAP tmp;        for(int i=0;i<m;i++){            scanf("%d%d%d",&a,&b,&c);            tmp.AddEdge(a,b,c);        }        res=tmp.Maxflow(1,n,n);        printf("%d\n",res);    }    return 0;}
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