poj 1463树形dp 树的最小覆盖

#include<iostream>
#include<cstdio>
#include<cstring>
#include<algorithm>
#include<queue>
#include<vector>
using namespace std;
// push_back 
inline int read(){
    int sum=0,x=1;
    char ch=getchar();
    while(ch<'0'||ch>'9'){
        if(ch=='-')
            x=0;
        ch=getchar();
    }
    while(ch>='0'&&ch<='9'){
        sum=(sum<<1)+(sum<<3)+(ch^48),ch=getchar();
    }
    return x?sum:-sum;
}
inline void write(int x){
    if(x<0)
        putchar('-'),x=-x;
    if(x>9)
        write(x/10);
    putchar(x%10+'0');
}
int mi(int x,int y){
    return x<y?x:y;
}
int ma(int x,int y){
    return x>y?x:y;
}
const int M=1505;
const int inf=0x3f3f3f3f;
vector<int>g[M];
int dp[M][2],f[M];
void dfs(int u){
    dp[u][0]=0,dp[u][1]=1;
    for(int i=0;i<g[u].size();i++){
        int v=g[u][i];
        dfs(v);
        dp[u][1]+=mi(dp[v][1],dp[v][0]);
        dp[u][0]+=dp[v][1];
    }
}
int main(){
    char ch,ch1,ch2;
    int n;
    while(~scanf("%d",&n)){
        for(int i=0;i<=n;i++)
            f[i]=0;
        for(int i=1;i<=n;i++){
            int u,k;
            scanf("%d:(%d)",&u,&k);
        //    cout<<k<<endl;
            u++;
            g[u].clear();
            while(k--){
                int v=read();
            //    cout<<"~~"<<v<<endl;
                v++;
                g[u].push_back(v);
                f[v]=u;
            //    son[u]=v;
            }
        }
        /*for(int i=1;i<=n;i++)

                dp[i][0]=0,dp[i][1]=1;*/
        int root=1;
        while(f[root])
            root=f[root];
        //cout<<root<<endl;
        dfs(root);
        write(mi(dp[root][0],dp[root][1]));
        putchar('\n');
    }
    return 0;
}