Luogu P2319 [HNOI2006]超级英雄

思路：二分图匹配；

提交：1次；

题解：如思路；

但是需要多记一个$ans[u]$代表匹配的答案。

#include<cstdio>
#include<iostream>
#include<cstring>
#define ull unsigned long long
#define ll long long
#define R register int
using namespace std;
#define pause (for(R i=1;i<=10000000000;++i))
#define In freopen("NOIPAK++.in","r",stdin)
#define Out freopen("out.out","w",stdout)
namespace Fread {
static char B[1<<15],*S=B,*D=B;
#ifndef JACK
#define getchar() (S==D&&(D=(S=B)+fread(B,1,1<<15,stdin),S==D)?EOF:*S++)
#endif
inline int g() {
    R ret=0,fix=1; register char ch; while(!isdigit(ch=getchar())) fix=ch=='-'?-1:fix;
    if(ch==EOF) return EOF; do ret=ret*10+(ch^48); while(isdigit(ch=getchar())); return ret*fix;
} inline bool isempty(const char& ch) {return (ch<=36||ch>=127);}
inline void gs(char* s) {
    register char ch; while(isempty(ch=getchar()));
    do *s++=ch; while(!isempty(ch=getchar()));
}
} using Fread::g; using Fread::gs;

namespace Luitaryi {
const int N=1010;
int n,m,cnt,C,tot;
int vr[N<<2],nxt[N<<2],fir[N],pre[N],ans[N],vis[N];
inline void add(int u,int v) {vr[++cnt]=v,nxt[cnt]=fir[u],fir[u]=cnt;}
inline bool dfs(int u) {
    for(R i=fir[u];i;i=nxt[i]) { R v=vr[i];
        if(vis[v]==C) continue; vis[v]=C;
        if(!pre[v]||dfs(pre[v])) {pre[v]=u,ans[u]=v; return true;}
    } return false;
}
inline void main() {
    n=g(),m=g();
    for(R i=1,x,y;i<=m;++i) x=g(),y=g(),add(i,x),add(i,y);
    for(R i=1;i<=m;++i) {
        ++C; if(dfs(i)) ++tot;
        else break;
    } printf("%d\n",tot);
    for(R i=1;i<=tot;++i) printf("%d\n",ans[i]);
}
}
signed main() {
    Luitaryi::main();
}

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2019.07.21