BZOJ3426 Poi2013 Tower Defense Game

每次任选一个没被覆盖的点就行……具体证明看commonc的博客把……懒得写了……

#include<iostream>
#include<cstdio>
#include<cstdlib>
#include<cstring>
#include<ctime>
#include<cmath>
#include<algorithm>
#include<iomanip>
#include<vector>
#include<map>
#include<set>
#include<bitset>
#include<queue>
#include<stack>
using namespace std;
#define MAXN 500010
#define MAXM 2000010
#define INF 1000000000
#define MOD 1000000007
#define eps 1e-8
#define ll long long
struct vec{
int to;
int fro;
};
vec mp[MAXM];
int tai[MAXN],cnt;
int n,m;
bool vis[MAXN],used[MAXN];
int ans[MAXN],ANS;
inline void be(int x,int y){
mp[++cnt].to=y;
mp[cnt].fro=tai[x];
tai[x]=cnt;
}
inline void bde(int x,int y){
be(x,y);
be(y,x);
}
void del(int x){
int i,y;
vis[x]=used[x]=1;
for(i=tai[x];i;i=mp[i].fro){
y=mp[i].to;
vis[y]=1;
}
}
int main(){
int i,x,y;
scanf("%d%d%*d",&n,&m);
for(i=1;i<=m;i++){
scanf("%d%d",&x,&y);
bde(x,y);
}
for(x=1;x<=n;x++){
if(!vis[x]){
ans[++ANS]=x;
del(x);
for(i=tai[x];i;i=mp[i].fro){
y=mp[i].to;
if(!used[y]){
del(y);
}
}
}
}
printf("%d\n",ANS);
for(i=1;i<=ANS;i++){
printf("%d ",ans[i]);
}
printf("\n");
return 0;
}

/*

*/