[BZOJ 2809][Apio2012]dispatching（左偏树）

#include<iostream>
#include<cstdio>
#include<cstdlib>
#include<cstring>
#define MAXN 100005
typedef long long LL;
using namespace std;
int n,m,b[MAXN],c[MAXN],l[MAXN],tot=0,root[MAXN];
LL ans=0;
struct Node
{
    int lch,rch,w,d,sz,sum;
}heap[MAXN];
void update(int x)
{
    heap[x].d=heap[heap[x].rch].d+1;
    heap[x].sz=heap[heap[x].lch].sz+heap[heap[x].rch].sz+1;
    heap[x].sum=heap[heap[x].lch].sum+heap[heap[x].rch].sum+heap[x].w;
}
int merge(int x,int y)
{
    if(!x||!y)return x+y;
    if(heap[x].w<heap[y].w)swap(x,y);
    heap[x].rch=merge(heap[x].rch,y);
    if(heap[heap[x].lch].d<heap[heap[x].rch].d)swap(heap[x].lch,heap[x].rch);
    update(x);
    return x;
}
int insert(int w)
{
    heap[++tot].d=0,heap[tot].sz=1;
    heap[tot].lch=heap[tot].rch=0;
    heap[tot].sum=heap[tot].w=w;
    return tot;
}
void pop(int &x)
{
    x=merge(heap[x].lch,heap[x].rch);
}
int main()
{
    scanf("%d%d",&n,&m);
    for(int i=1;i<=n;i++)
    {
        scanf("%d%d%d",&b[i],&c[i],&l[i]);
        root[i]=insert(c[i]);
        while(heap[root[i]].sum>m)pop(root[i]);
    }
    for(int i=n;i>0;i--)
    {
        ans=max(ans,1LL*heap[root[i]].sz*l[i]);
        root[b[i]]=merge(root[i],root[b[i]]);
        while(heap[root[b[i]]].sum>m)pop(root[b[i]]);
    }
    printf("%lld",ans);
    return 0;
}