图论：带花树算法-一般图最大匹配

一般图匹配就是给一般图像二分图那样做最大匹配

问你最大能匹配多少对，带花树算法的过程这里不再描述

直接上模板

//It is made by ljh2000
#include <iostream>
#include <cstdlib>
#include <cstring>
#include <cstdio>
#include <cmath>
#include <algorithm>
using namespace std;
typedef long long LL;
const int MAXN = 520;
const int MAXM = 250011;
const int MAXL = 10011;
int n,m,ecnt,first[MAXN],next[MAXM],to[MAXM],father[MAXN],Tim;
int dui[MAXL],head,tail,id[MAXN],pre[MAXN],match[MAXN],ans,vis[MAXN];
inline int find(int x){ if(father[x]!=x) father[x]=find(father[x]); return father[x]; }
inline int getint(){
    int w=0,q=0; char c=getchar(); while((c<'0'||c>'9') && c!='-') c=getchar();
    if(c=='-') q=1,c=getchar(); while (c>='0'&&c<='9') w=w*10+c-'0',c=getchar(); return q?-w:w;
}
 
inline int lca(int x,int y){
    Tim++;
    while(vis[x]!=Tim) {
        if(x) {
            x=find(x);
            if(vis[x]==Tim) return x;
            vis[x]=Tim;
            if(match[x]!=0) x=find(pre[match[x]]);
            else x=0;
        }
        swap(x,y);
    }
    return x;
}
 
inline void change(int x,int y,int k){//把奇环上的点缩成一个点，并且把原来是奇点的点变成偶点，加入队列
    while(find(x)!=k) {
        pre[x]=y; int z=match[x];
        if(id[z]==1) { id[z]=0; dui[++tail]=z; }
        if(find(z)==z) father[z]=k;
        if(find(x)==x) father[x]=k;
        y=z; x=pre[y];
    }
}
 
inline bool bfs(int ini){
    for(int i=1;i<=n;i++) id[i]=-1,father[i]=i;
    head=tail=0; dui[++tail]=ini; id[ini]=0; int u;
    while(head<tail) {
        u=dui[++head];
        for(int i=first[u];i;i=next[i]) {
            int v=to[i];
            if(id[v]==-1) {
                pre[v]=u; id[v]=1;
                if(!match[v]) {
                    int last,t,now=v;
                    while(now!=0) {
                        t=pre[now]; last=match[t];
                        match[t]=now; match[now]=t;
                        now=last;
                    }
                    return true;
                }
                id[match[v]]=0; dui[++tail]=match[v];
            }
            else if(id[v]==0&&find(u)!=find(v)){ //出现奇环且不是在同一个环中
                int g=lca(u,v);
                change(u,v,g);
                change(v,u,g);
            }
        }
    }
    return false;
}
 
inline void work(){
    n=getint(); m=getint(); int x,y;
    for(int i=1;i<=m;i++) {
        x=getint(); y=getint();
        next[++ecnt]=first[x]; first[x]=ecnt; to[ecnt]=y;
        next[++ecnt]=first[y]; first[y]=ecnt; to[ecnt]=x;
    }
    for(int i=1;i<=n;i++) if(!match[i]&&bfs(i)) ans++;
    printf("%d
",ans);
    for(int i=1;i<=n;i++) printf("%d ",match[i]);
}
 
int main()
{
    work();
    return 0;
}