[bzoj] 2809 dispatching

#include<cstdio>
#include<algorithm>
#define N 100010
typedef long long ll;
using namespace std;
int n,m,f[N],cnt=1,l,r,q[N],money[N],lead[N],head[N];
ll ans;
struct node
{
    node *ls,*rs;
    int dis,sze,val;
    ll sum;
    node(): ls(NULL), rs(NULL), dis(0), sze(0), val(0), sum(0){}
    node(int x): ls(NULL), rs(NULL), dis(0), sze(1), val(x), sum(x){}
    node *updt()
    {
        if(!ls || ls->dis<rs->dis) swap(ls,rs);
        dis=rs?rs->dis+1:0;
        sze=(ls?ls->sze:0)+(rs?rs->sze:0)+1;
        sum=(ls?ls->sum:0)+(rs?rs->sum:0)+val;
        return this;
    }
}*tre[N];
struct hhh
{
    int to,next;
}edge[N];

int read()
{
    int ans=0,fu=1;
    char j=getchar();
    for (;(j<‘0‘ || j>‘9‘) && j!=‘-‘;j=getchar()) ;
    if (j==‘-‘) fu=-1,j=getchar();
    for (;j>=‘0‘ && j<=‘9‘;j=getchar()) ans*=10,ans+=j-‘0‘;
    return ans*fu;
}

void add(int u,int v)
{
    edge[cnt].to=v;
    edge[cnt].next=head[u];
    head[u]=cnt++;
}

node *merge(node* x,node* y)
{
    if (!x) return y;
    if (!y) return x;
    if (x->val<y->val) swap(x,y);
    x->rs=merge(x->rs,y);
    return x->updt();
}

void pop(node* &x)
{
    while (x->sum>m)
    x=merge(x->ls,x->rs);
}

int main()
{
    n=read();
    m=read();
    for (int i=1;i<=n;i++)
    {
    f[i]=read();
    money[i]=read();
    lead[i]=read();
    add(f[i],i);
    tre[i]=new node(money[i]);
    }
    q[++r]=1;
    for (int l=1;l<=r;l++)
    for (int e=head[q[l]];e;e=edge[e].next)
        q[++r]=edge[e].to;
    for (int l=r,v,u;l>=1;l--)
    {
    v=q[l];
    u=f[v];
    ans=max(ans,(ll)lead[v]*tre[v]->sze);
    if (u) tre[u]=merge(tre[u],tre[v]),pop(tre[u]);
    }
    printf("%lld\n",ans);
    return 0;
}