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Open cup 2019 Korea Gym 102059A Coloring Roads

樹鏈剖分。
先做輕重鏈剖分後,維護每一條鏈上的資訊。初始樹為空。
以每一條重鏈的頭top為基點,建立單調棧。棧內維護,從大到小,該鏈上修改的深度,以及對應顏色。
每一次修改,如果棧內有比他淺的點,即,若我們把當前的顏色塗上,會使得之前的顏色覆蓋掉,故我們清除掉該顏色。不斷彈棧,直到為空或者棧頂比他深度深。若棧頂比他深,優先修改,當前的顏色的深度,即,把深度更深的顏色,給修改為空,我們才能重新計算並且塗上顏色。
然後每一個跳top的father的時候,我們單獨把所有的,這樣的top-father拿出來計算即可。

#include<iostream>
#include<cstring>
#include<algorithm>
#include<cmath>
#include<cstdlib>
#include<climits>
#include<stack>
#include<vector>
#include<queue>
#include<set>
#include<bitset>
#include<map>
//#include<regex>
#include<cstdio>
#include <iomanip>
#pragma GCC optimize(2)
#define up(i,a,b)  for(int i=a;i<b;i++)
#define dw(i,a,b)  for(int i=a;i>b;i--)
#define upd(i,a,b) for(int i=a;i<=b;i++)
#define dwd(i,a,b) for(int i=a;i>=b;i--)
//#define local
typedef long long ll;
typedef unsigned long long ull;
const double esp = 1e-6;
const double pi = acos(-1.0);
const int INF = 0x3f3f3f3f;
const int inf = 1e9;
using namespace std;
int read()
{
	char ch = getchar(); int x = 0, f = 1;
	while (ch<'0' || ch>'9') { if (ch == '-')f = -1; ch = getchar(); }
	while (ch >= '0' && ch <= '9') { x = x * 10 + ch - '0'; ch = getchar(); }
	return x * f;
}
typedef pair<int, int> pir;
#define lson l,mid,root<<1
#define rson mid+1,r,root<<1|1
#define lrt root<<1
#define rrt root<<1|1
const int N = 2e5 + 10;
vector<int>g[N];
int u, v, n, q, c, m, cr;
int col[N], cnt[N];
int id_s = 0;
int id[N], siz[N], son[N], top[N], f[N];
//int eg[N];
//int rk[N];
vector<pir>s[N];
void dfs1(int now, int fa, int d)
{
	//rk[u] = ++tot_;
	f[now] = fa;
	//dep[u] = d;
	siz[now] = 1;
	for (auto k : g[now])
	{
		if (k == fa)continue;
		dfs1(k, now, d + 1);
		siz[now] += siz[k];
		if (siz[son[now]] < siz[k])
		{
			son[now] = k;
		}
	}
	return;
}
void dfs2(int now, int tp)
{
	id[now] = ++id_s;
	top[now] = tp;
	if (son[now])
	{
		dfs2(son[now], tp);
	}
	for (auto k : g[now])
	{
		if (k == f[now] || k == son[now])continue;
		dfs2(k, k);
	}
	return;
}
void modify(int val, int c)
{
	cnt[col[c]]--;
	col[c] += val;
	cnt[col[c]]++;
}
void update(int l, int r, int c)
{

}
int main()
{
	scanf("%d %d %d", &n, &cr, &q);
	upd(i, 1, n - 1)
	{
		scanf("%d %d", &u, &v);
		g[u].push_back(v);
		g[v].push_back(u);
	}
	cnt[0] = cr;
	//col[0] = n - 1;
	//num[n - 1] = 1;
	dfs1(1, 0, 1);
	dfs2(1, 1);
	while (q--)
	{
		scanf("%d %d %d", &u, &v, &m);
		while (u)
		{
			int tp = top[u];
			int pr = id[tp] - 1;
			while (!s[tp].empty() && s[tp].back().first < id[u])
			{
				pir temp = s[tp].back();
				s[tp].pop_back();
				modify(-(temp.first - pr), temp.second);
				pr = temp.first;
			}
			if (!s[tp].empty())
			{
				modify(-(id[u] - pr), s[tp].back().second);
			}
			s[tp].push_back(make_pair(id[u], v));
			modify(id[u] - id[tp] + 1, v);
			u = f[tp];
			//if (u == 0)break;
		}
		int ans = cnt[m];
		if (col[v] == m)ans--;
		else if (col[v] == m + 1)ans++;
		printf("%d\n", ans);
	}
	return 0;
}