hdu3290 DFS

来源：互联网发布：java认证考试报名编辑：程序博客网时间：2024/06/06 00:36
也算树形dp？~~
#include <iostream>#include <cstdio>#include <cstring>#include <algorithm>using namespace std;const int MAXN=30000;const int MAXM=50000;struct node{    int u,v;};node edge[MAXM];int first[MAXN],next[MAXM];int cc;int num[MAXN];int child_num[MAXN];int in[MAXN];inline void add_edge(int u,int v){    edge[cc].u=u;    edge[cc].v=v;    next[cc]=first[u];    first[u]=cc;    cc++;}void dfs(int u){    if(num[u]!=-1)        return ;    int i;    int k=0;    int *temp=new int[MAXN];    for(i=first[u];i!=-1;i=next[i])    {        int v=edge[i].v;        dfs(v);        temp[k++]=num[v];    }    sort(temp,temp+k);    num[u]=temp[(child_num[u]+1)/2-1];    delete temp;    return ;}void Scan(int &num)    //对G++使用{    char in;    bool neg=false;    while(((in=getchar()) > '9' || in<'0') && in!='-') ;    if(in=='-')    {        neg=true;        while((in=getchar()) >'9' || in<'0');    }    num=in-'0';    while(in=getchar(),in>='0'&&in<='9')        num*=10,num+=in-'0';    if(neg)        num=0-num;}int main(){    int n;    while(scanf("%d",&n)!=EOF)    {        int i;        memset(first,-1,sizeof(first));        memset(next,-1,sizeof(next));        cc=0;        memset(num,-1,sizeof(num));        memset(in,0,sizeof(in));        memset(child_num,0,sizeof(child_num));        for(i=1;i<=n;i++)        {            int p;            Scan(p);            child_num[i]=p;            if(p==0)                num[i]=i;            int j;            for(j=0;j<p;j++)            {                int x;                Scan(x);                in[x]++;                add_edge(i,x);            }        }        for(i=1;i<=n;i++)            if(in[i]==0)            {                dfs(i);                break;            }        printf("%d\n",num[i]);    }    return 0;}