luogu3386 【模板】二分图匹配 匈牙利算法 hdu2063 过山车 dinic

luogu

匈牙利算法

#include <iostream>
#include <cstring>
#include <cstdio>
using namespace std;
int n, m, uu, vv, e, lnk[1005], ans;
bool a[1005][1005], vis[1005];
bool dfs(int u){
    for(int i=1; i<=m; i++){
        if(a[u][i] && !vis[i]){
            vis[i] = true;
            if(!lnk[i] || dfs(lnk[i])){
                lnk[i] = u;
                return true;
            }
        }
    }
    return false;
}
int main(){
    cin>>n>>m>>e;
    for(int i=1; i<=e; i++){
        scanf("%d %d", &uu, &vv);
        if(uu>n || vv>m)    continue;
        a[uu][vv] = true;
    }
    for(int i=1; i<=n; i++){
        memset(vis, 0, sizeof(vis));
        if(dfs(i))  ans++;
    }
    cout<<ans<<endl;
    return 0;
}

hdu

建图最大流dinic

#include <iostream>
#include <cstring>
#include <cstdio>
#include <queue>
using namespace std;
struct Edge{
    int too, nxt, val;
}edge[4005];
int k, m, n, ss, tt, cnt, hea[1005], uu, vv, maxFlow, lev[1005];
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));
    d.push(ss);
    lev[ss] = 1;
    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;
}
void dinic(){
    while(bfs())    maxFlow += dfs(ss, oo);
}
int main(){
    while(scanf("%d", &k)!=EOF){
        if(!k)  break;
        scanf("%d %d", &m, &n);
        ss = 0; tt = m + n + 1;
        memset(hea, -1, sizeof(hea));
        cnt = maxFlow = 0;
        for(int i=1; i<=k; i++){
            scanf("%d %d", &uu, &vv);
            add_edge(uu, vv+m, 1);
            add_edge(vv+m, uu, 0);
        }
        for(int i=1; i<=m; i++){
            add_edge(ss, i, 1);
            add_edge(i, ss, 0);
        }
        for(int i=m+1; i<=m+n; i++){
            add_edge(i, tt, 1);
            add_edge(tt, i, 0);
        }
        dinic();
        printf("%d\n", maxFlow);
    }
    return 0;
}