最大流

最大流模版EdmondsKarp算法, (刘汝佳算法竞赛入门经典)

#include <cstdio>//C语言io#include <cstring>//以下是c语言常用头文件#include <cmath>#include <cstdlib>#include <ctime>#include <cctype>#include <cstring>#include <cmath>#include <iostream>//c++IO#include <sstream>#include <string>#include <list>//c++常用容器#include <vector>#include <set>#include <map>#include <queue>#include <stack>#include <algorithm>//c++泛型的一些函数#include <functional>//用来提供一些模版#define fo0(i,n) for(int i = 0;i < n; ++i)#define fo1(i,n) for(int i = 1;i <= n; ++i)#define mem(ar,num) memset(ar,num,sizeof(ar))#define me(ar) memset(ar,0,sizeof(ar))#define lowbit(x) (x&(-x))using namespace std;typedef long long LL;typedef unsigned long long ULL;const int    prime = 999983;const int    INF = 0x7FFFFFFF;const LL     INFF =0x7FFFFFFFFFFFFFFF;const double pi = acos(-1.0);const double inf = 1e18;const double eps = 1e-6;const LL     mod = 1e9 + 7;//......................................................const int maxn = 500+100;struct Edge{  int from,to,cap,flow;  Edge(int u,int v,int c,int f):from(u),to(v),cap(c),flow(f){}};struct EK{  int n,m;  vector<Edge> edges;  vector<int> G[maxn];  int a[maxn];  int p[maxn];  void init(int n)  {      for(int i = 0;i < n; ++i)        G[i].clear();  }  void AddEdge(int from,int to,int cap)  {      edges.push_back(Edge(from,to,cap,0));      edges.push_back(Edge(from,to,0,0));      m = edges.size();      G[from].push_back(m-2);      G[to].push_back(m-1);  }  int Maxflow(int s,int t)  {      int flow = 0;      while(1)      {          me(a);          queue<int> Q;          Q.push(s);          a[s] = INF;          while(!Q.empty())          {              int x = Q.front();Q.pop();              for(size_t i = 0;i < G[x].size();++i)              {                  Edge& e = edges[G[x][i]];                  if(!a[e.to]&&e.cap>e.flow)                  {                      p[e.to] = G[x][i];                      a[e.to] = min(a[x],e.cap-e.flow);                      Q.push(e.to);                  }              }              if(a[t])                    break;          }          if(!a[t])            break;          flow += a[t];          for(int  u = t; u != s;u = edges[p[u]].from)          {              edges[p[u]].flow += a[t];              edges[p[u]^1].flow -= a[t];          }      }      return flow;  }};int main(){   int n,m;   EK ek;   while(cin>>n>>m)   {       ek.init(n);       int u,v,w;       while(m--)       {           scanf("%d %d %d",&u,&v,&w);           ek.AddEdge(u,v,w);       }       printf("%d\n",ek.Maxflow(1,n));   }    return 0;}

最小花费最大流

const int LEN_of_Node = 5000+10;const int LEN_of_Edge = 100000;const int maxn = 1e9;struct Edge{    int from,to,cap,flow,cost;    Edge(int u,int v,int c,int f,int w):from(u),to(v),cap(c),flow(f),cost(w){};};struct EK{    int n,m;    vector<Edge> edges;    vector<int> G[LEN_of_Node];    int inq[LEN_of_Node];    int p[LEN_of_Node];    int a[LEN_of_Node];    int dis[LEN_of_Node];    void init(int n)    {        this->n = n;        for(int i = 0;i < n; ++i)            G[i].clear();        edges.clear();    }    void AddEdge(int from,int to,int cap,int cost)    {       edges.push_back(Edge(from,to,cap,0,cost));       edges.push_back(Edge(to,from,0,0,-cost));       m = edges.size();       G[from].push_back(m-2);       G[to].push_back(m-1);    }    bool BellmanFord(int s,int t,int &flow,long long &cost)    {       for(int i = 0;i < n; ++i)        dis[i] = maxn ;       dis[s] = 0;       me(inq);       inq[s] = 1;       a[s] = maxn;       queue<int> Q;       Q.push(s);       while(!Q.empty())       {           int q = Q.front();           Q.pop();           inq[q] = 0;           for(size_t i = 0;i < G[q].size();++i)           {               Edge &tmp = edges[G[q][i]];               if(tmp.cap>tmp.flow&&dis[tmp.to] > dis[q] + tmp.cost)               {                   dis[tmp.to] = dis[q] + tmp.cost;                   a[tmp.to] = min(a[q],tmp.cap-tmp.flow);                   p[tmp.to] = G[q][i];                   if(!inq[tmp.to])                   {                       inq[tmp.to] = 1;                       Q.push(tmp.to);                   }               }           }       }       if(dis[t]==maxn)        return false;       flow += a[t];       cost += (LL) a[t]*(LL)dis[t];       for(int u = t; u != s; u = edges[p[u]].from)       {           edges[p[u]].flow += a[t];           edges[p[u]^1].flow -= a[t];       }//       for(int now = p[t];now; now = p[edges[now].from] )//       {//           edges[now].flow += a[t];//           edges[now^1].flow -= a[t];//       }       return true;    }    void MincostMaxflow(int s,int t,int &flow,long long &cost)    {        flow = 0;        cost = 0;        while(BellmanFord(s,t,flow,cost));    }};EK ek;int main(void){//     cout<<INT_MAX<<endl;    int N,M,S,T;    while(cin>>N>>M>>S>>T)    {       ek.init(N);       int u,v,w,c;       for(int i = 0;i < M; ++i)       {           scanf("%d %d %d %d",&u,&v,&w,&c);           ek.AddEdge(u,v,w,c);       }       int flow;       LL ans;       ek.MincostMaxflow(S,T,flow,ans);       printf("%d %lld\n",flow,ans);    }    return 0;}