HDU1054 Strategic Game

Questions surface: http://acm.hdu.edu.cn/showproblem.php?pid=1054

本题是求树的最小点覆盖裸题。

Code:
#include<iostream>
#include<cstdio>
#include<cmath>
#include<cstring>
#include<cstdlib>
#include<algorithm>
#include<ctime>
using namespace std;
const int N=6005;
int n,f[N][2],Head[N],Cnt;
bool vis[N];
struct Node{
    int v,Next;
}Edge[N*2];
void Push(int u,int v){
    ++Cnt;
    Edge[Cnt].v=v;
    Edge[Cnt].Next=Head[u];
    Head[u]=Cnt;
}
void dfs(int u,int fa){
    f[u][0]=0;
    f[u][1]=1;
    for(int i=Head[u];i;i=Edge[i].Next){
        int v=Edge[i].v;
        if(v==fa){
            continue;
        }
        dfs(v,u);
        f[u][0]+=f[v][1];
        f[u][1]+=min(f[v][0],f[v][1]);
    }
}
int main(){
    while(~scanf("%d",&n)){
        memset(Head,0,sizeof(Head));
        Cnt=0;
        for(int i=1;i<=n;i++){
            int u,k;
            scanf("%d:(%d)",&u,&k);
            u++;
            for(int j=1;j<=k;j++){
                int v;
                scanf("%d",&v);
                v++;
                Push(u,v);
                Push(v,u);
            }
        }
        memset(f,0,sizeof(f));
        dfs(1,0);
        printf("%d\n",min(f[1][0],f[1][1]));
    }
    return 0;
}