Hdu2196 Computer (tree DP)

It's a classic tree-DP title
debugging for a night, plus a morning, WA numerous times
and finally found turned out to be multiple sets of input! ! ! ! !
I'm furious!
How much wasted time!
Really served, with wide seeing vain "Input file contains multiple test cases"
finally added a while (scanf) before. . . . .

There are two answers to each node, this is a sub-tree node to its longest distance of a point, and one of the longest distance on the direction of its parent node

Code:

#include <bits/stdc++.h>
#define ll long long
using namespace std;

const int MaxSize = 10005;

struct node
{
    ll w,to,next;
}q[10005];
ll head[MaxSize],d[MaxSize][3];

void dfs1(ll n)
{
    ll st[10005],j=0;
    for(int i=head[n];i!=-1;i=q[i].next)
    {
        dfs1(q[i].to);
        d[n][0]=max(d[n][0],d[q[i].to][0]+q[i].w);
        st[j++]=d[q[i].to][0]+q[i].w;
    }
    sort(st,st+j);
    if(j>1)
    {d[n][1]=st[j-2];}
    return ;
}
void dfs2(ll n,ll f,ll w)
{
    if(n!=f)
    {
        ll op=d[n][0]+w;
        if(op==d[f][0])
        {
            d[n][2]=max(d[n][2],d[f][2]+w);
            d[n][2]=max(d[n][2],d[f][1]+w);
        }
        else
        {
            d[n][2]=max(d[n][2],d[f][2]+w);
            d[n][2]=max(d[n][2],d[f][0]+w);
        }
    }
    for(int i=head[n];i!=-1;i=q[i].next)
    {
        dfs2(q[i].to,n,q[i].w);
    }
    return ;
}

int main()
{
    ll n,a,b;
    while(~scanf("%lld",&n)){
    
    memset(head,-1,sizeof(head));
    memset(d,0,sizeof(d));
    
    ll cnt=1;
    for(int i=2;i<=n;i++)
    {
        scanf("%lld %lld",&a,&b);
        q[cnt].to=i;
        q[cnt].w=b;
        q[cnt].next=head[a];
        head[a]=cnt;
        cnt++;
    }
    dfs1(1);
    dfs2(1,1,0);
    for(int i=1;i<=n;i++)
    {
        cout<<max(d[i][0],d[i][2])<<endl;
    }
    }
    return 0;
}