luogu3376 模板网络最大流 dinic

Posted 2020-10-18 poorpool

当前弧优化、单路增广

#include <iostream>
#include <cstring>
#include <cstdio>
#include <queue>
using namespace std;
int n, m, ss, tt, uu, vv, ww, cnt, hea[10005], maxFlow, cur[10005], lev[10005];
const int oo=0x3f3f3f3f;
queue<int> d;
struct Edge{
    int too, nxt, val;
}edge[200005];
void add_edge(int fro, int too, int val){
    edge[cnt].nxt = hea[fro];
    edge[cnt].too = too;
    edge[cnt].val = val;
    hea[fro] = cnt++;
}
bool bfs(){
    memset(lev, 0, sizeof(lev));
    lev[ss] = 1;
    d.push(ss);
    while(!d.empty()){
        int x=d.front();
        d.pop();
        for(int i=hea[x]; i!=-1; i=edge[i].nxt){
            int t=edge[i].too;
            if(!lev[t] && edge[i].val>0){
                d.push(t);
                lev[t] = lev[x] + 1;
            }
        }
    }
    return lev[tt]!=0;
}
int dfs(int x, int lim){
    if(x==tt)   return lim;
    for(int &i=cur[x]; i!=-1; i=edge[i].nxt){
        int t=edge[i].too;
        if(lev[t]==lev[x]+1 && edge[i].val>0){
            int temp=dfs(t, min(lim, edge[i].val));
            if(temp>0){
                edge[i].val -= temp;
                edge[i^1].val += temp;
                return temp;
            }
        }
    }
    return 0;
}
void dinic(){
    while(bfs()){
        for(int i=1; i<=n; i++) cur[i] = hea[i];
        int temp;
        while(temp=dfs(ss, oo)) maxFlow += temp;
    }
}
int main(){
    cin>>n>>m>>ss>>tt;
    memset(hea, -1, sizeof(hea));
    for(int i=1; i<=m; i++){
        scanf("%d %d %d", &uu, &vv, &ww);
        add_edge(uu, vv, ww);
        add_edge(vv, uu, 0);
    }
    dinic();
    cout<<maxFlow<<endl;
    return 0;
}

裸dinic

#include <iostream>
#include <cstring>
#include <cstdio>
#include <queue>
using namespace std;
struct Edge{
    int too, nxt, val;
}edge[200005];
int n, m, uu, vv, ww, cnt=0, maxFlow, hea[10005], ss, tt, lev[10005];
const int oo=0x3f3f3f3f;
queue<int> d;
void add_edge(int fro, int too, int val){
    edge[cnt].nxt = hea[fro];
    edge[cnt].too = too;
    edge[cnt].val = val;
    hea[fro] = cnt++;
}
bool bfs(){
    memset(lev, 0, sizeof(lev));
    lev[ss] = 1;
    d.push(ss);
    while(!d.empty()){
        int x=d.front();
        d.pop();
        for(int i=hea[x]; i!=-1; i=edge[i].nxt){
            int t=edge[i].too;
            if(!lev[t] && edge[i].val>0){
                lev[t] = lev[x] + 1;
                d.push(t);
            }
        }
    }
    return lev[tt]!=0;
}
int dfs(int x, int lim){
    if(x==tt)   return lim;
    int addFlow=0;
    for(int i=hea[x]; i!=-1 && addFlow<lim; i=edge[i].nxt){
        int t=edge[i].too;
        if(lev[t]==lev[x]+1 && edge[i].val>0){
            int tmp=dfs(t, min(lim-addFlow, edge[i].val));
            edge[i].val -= tmp;
            edge[i^1].val += tmp;
            addFlow += tmp;
        }
    }
    return addFlow;
}
int main(){
    cin>>n>>m>>ss>>tt;
    memset(hea, -1, sizeof(hea));
    for(int i=1; i<=m; i++){
        scanf("%d %d %d", &uu, &vv, &ww);
        add_edge(uu, vv, ww);
        add_edge(vv, uu, 0);
    }
    while(bfs())    maxFlow += dfs(ss, oo);
    cout<<maxFlow<<endl;
    return 0;
}