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| #include <cstdio>
#include <algorithm>
#include <vector>
using namespace std;
template <class Type>
void read(Type &x)
{
char c;
bool flag = false;
while ((c = getchar()) < '0' || c > '9')
c == '-' && (flag = true);
x = c - '0';
while ((c = getchar()) >= '0' && c <= '9')
x = (x << 3) + (x << 1) + c - '0';
if (flag) x = ~x + 1;
}
template <class Type, class ...rest>
void read(Type &x, rest &...y) { read(x), read(y...); }
template <class Type>
void write(Type x)
{
if (x < 0) putchar('-'), x = ~x + 1;
if (x > 9) write(x / 10);
putchar(x % 10 + '0');
}
void chkmin (int &x, int k) { if (k < x) x = k; }
void chkmax (int &x, int k) { if (k > x) x = k; }
typedef long long LL;
typedef pair <int, int> PII;
const int N = 1e5 + 10, M = 2e5 + 10;
bool vis[N];
int n, m, g;
LL tr[N];
int idx, hd[N], nxt[M], edg[M], wt[M];
void modify (int x, int k)
{
for (++x; x <= g; x += x & -x)
tr[x] += k;
}
LL query (int x)
{
int res = 0;
for (++x; x > 0; x -= x & -x)
res += tr[x];
return res;
}
int Size (int x, int fa)
{
if (vis[x]) return 0;
int res = 1;
for (int i = hd[x]; i; i = nxt[i])
if (edg[i] ^ fa) res += Size(edg[i], x);
return res;
}
int WeightCentre (int x, int fa, int tot, int &wc)
{
if (vis[x]) return 0;
int sum = 1, mx = 0;
for (int i = hd[x]; i; i = nxt[i]) if (edg[i] ^ fa)
{
int t = WeightCentre(edg[i], x, tot, wc);
chkmax(mx, t), sum += t;
}
chkmax(mx, tot - sum);
if (mx <= tot / 2) wc = x;
return sum;
}
void Dist (int x, int fa, int s, int t, vector<PII> &q)
{
if (vis[x]) return;
q.push_back(make_pair(s, t));
for (int i = hd[x]; i; i = nxt[i])
if (edg[i] ^ fa) Dist(edg[i], x, s + wt[i], t + 1, q);
}
LL get (vector<PII> p)
{
sort(p.begin(), p.end());
LL res = 0;
int i = p.size(), j = 0;
while (~--i)
{
while (j < i && p[j].first + p[i].first <= m)
modify(p[j++].second, 1);
if (j > i) modify(p[--j].second, -1);
res += query(g - p[i].second);
}
return res;
}
LL calc (int x)
{
if (vis[x]) return 0;
WeightCentre(x, -1, Size(x, -1), x);
vis[x] = true;
LL res = 0;
vector <PII> p;
p.push_back(make_pair(0, 0));
for (int i = hd[x]; i; i = nxt[i])
{
vector <PII> q;
Dist(edg[i], -1, wt[i], 1, q);
res -= get(q);
for (PII k : q) p.push_back(k);
}
res += get(p);
for (int i = hd[x]; i; i = nxt[i]) res += calc(edg[i]);
return res;
}
void add (int a, int b, int c)
{
nxt[++idx] = hd[a];
hd[a] = idx;
edg[idx] = b;
wt[idx] = c;
}
int main()
{
read(n, g, m);
for (int i = 1, p, w; i < n; i++)
read(p, w), add(i + 1, p, w), add(p, i + 1, w);
write(calc(1));
return 0;
}
|