BZOJ2809 [Apio2012]dispatching

/**************************************************************
Problem: 2809
User: rausen
Language: C++
Result: Accepted
Time:804 ms
Memory:7624 kb
****************************************************************/

#include <cstdio>
#include <algorithm>

using namespace std;
typedef long long ll;
const int N = 100005;

struct heap{
int v, l, r, dep;
}h
;
int cnt_heap;

struct edge {
int next, to;
edge() {}
edge(int _n, int _t) : next(_n), to(_t) {}
} e
;
int first
, tot;

struct tree_node {
int cost, l, root;
ll sum, sz;
} tr
;

int n, m;
ll ans;

inline int read() {
int x = 0, sgn = 1;
char ch = getchar();
while (ch < '0' || '9' < ch) {
if (ch == '-') sgn = -1;
ch = getchar();
}
while ('0' <= ch && ch <= '9') {
x = x * 10 + ch - '0';
ch = getchar();
}
return sgn * x;
}

inline void add_edge(int x, int y) {
e[++tot] = edge(first[x], y);
first[x] = tot;
}

inline int new_heap(int x) {
h[++cnt_heap].v = x;
h[cnt_heap].l = h[cnt_heap].r = h[cnt_heap].dep = 0;
return cnt_heap;
}

int Merge(int x, int y) {
if (!x || !y) return x + y;
if (h[x].v < h[y].v)
swap(x, y);
h[x].r = Merge(h[x].r, y);
if (h[h[x].l].dep < h[h[x].r].dep)
swap(h[x].l, h[x].r);
h[x].dep = h[h[x].r].dep + 1;
return x;
}

inline int Top(int p) {
return h[p].v;
}

void Pop(int &p) {
p = Merge(h[p].l, h[p].r);
}

void dfs(int p) {
int x, y;
tr[p].root = new_heap(tr[p].cost);
tr[p].sum = tr[p].cost, tr[p].sz = 1;
for (x = first[p]; x; x = e[x].next) {
dfs(y = e[x].to);
tr[p].sum += tr[y].sum, tr[p].sz += tr[y].sz;
tr[p].root = Merge(tr[p].root, tr[y].root);
}
while (tr[p].sum > m) {
tr[p].sum -= Top(tr[p].root), Pop(tr[p].root);
--tr[p].sz;
}
ans = max(ans, tr[p].sz * tr[p].l);
}

int main() {
int i, x;
n = read(), m = read();
for (i = 1; i <= n; ++i) {
x = read();
add_edge(x, i);
tr[i].cost = read(), tr[i].l = read();
}
dfs(1);
printf("%lld\n", ans);
return 0;
}