gistfile1.cpp

//Ford-Fulkerson's algorithm
struct edge{int to,cap,rev;};
const int INF=1e9;

//g[e.to][e.rev] で逆辺を操作できる
void addEdge(vector<vector<edge> > &g,int from,int to,int cap){
    g[from].push_back((edge){to,cap,(int)g[to].size()});
    g[to].push_back((edge){from,0,(int)g[from].size()-1});
}
int dfs(vector<vector<edge> > &g,vector<bool> &used,int v,int t,int f){
    if(v==t) return f;
    used[v]=true;
    for(int i=0;i<(int)g[v].size();i++){
        edge& e=g[v][i];
        if(!used[e.to] && e.cap>0){
            int d=dfs(g,used,e.to,t,min(f,e.cap));
            if(d>0){
                e.cap-=d;
                g[e.to][e.rev].cap+=d;
                return d;
            }
        }
    }
    return 0;
}
int FordFulkerson(vector<vector<edge> > &g,int s,int t){
    int flow=0;
    for(;;){
        vector<bool> used(g.size(),false);
        int f=dfs(g,used,s,t,INF);
        if(f==0) return flow;
        flow+=f;
    }
}