Query on a tree 树链剖分 [模板]

#include<iostream>
#include<cstdio>
#include<algorithm>
#include<cstdlib>
#include<cstring>
#include<string>
#include<cmath>
#include<map>
#include<set>
#include<vector>
#include<queue>
#include<bitset>
#include<ctime>
#include<deque>
#include<stack>
#include<functional>
#include<sstream>
//#include<cctype>
//#pragma GCC optimize(2)
using namespace std;
#define maxn 100005
#define inf 0x7fffffff
//#define INF 1e18
#define rdint(x) scanf("%d",&x)
#define rdllt(x) scanf("%lld",&x)
#define rdult(x) scanf("%lu",&x)
#define rdlf(x) scanf("%lf",&x)
#define rdstr(x) scanf("%s",x)
#define mclr(x,a) memset((x),a,sizeof(x))
typedef long long  ll;
typedef unsigned long long ull;
typedef unsigned int U;
#define ms(x) memset((x),0,sizeof(x))
const long long int mod = 1e9;
#define Mod 1000000000
#define sq(x) (x)*(x)
#define eps 1e-5
typedef pair<int, int> pii;
#define pi acos(-1.0)
//const int N = 1005;
#define REP(i,n) for(int i=0;i<(n);i++)
typedef pair<int, int> pii;

inline int rd() {
	int x = 0;
	char c = getchar();
	bool f = false;
	while (!isdigit(c)) {
		if (c == ‘-‘) f = true;
		c = getchar();
	}
	while (isdigit(c)) {
		x = (x << 1) + (x << 3) + (c ^ 48);
		c = getchar();
	}
	return f ? -x : x;
}


ll gcd(ll a, ll b) {
	return b == 0 ? a : gcd(b, a%b);
}
int sqr(int x) { return x * x; }



/*ll ans;
ll exgcd(ll a, ll b, ll &x, ll &y) {
	if (!b) {
		x = 1; y = 0; return a;
	}
	ans = exgcd(b, a%b, x, y);
	ll t = x; x = y; y = t - a / b * y;
	return ans;
}
*/
struct node {
	int to, nxt;
}e[maxn];
int head[maxn], tot;
int top[maxn];// top[v]表示v所在的重链的顶点
int fa[maxn];
int dep[maxn];
int num[maxn];// num[v]表示以v为根的子树大小
int p[maxn];// p[v]表示v与其父亲节点在线段树的位置
int fp[maxn];
int son[maxn];// 重儿子
int pos;
int n;

void init() {
	tot = 0; memset(head, -1, sizeof(head));
	pos = 1; memset(son, -1, sizeof(son));
}
void addedge(int u, int v) {
	e[tot].to = v; e[tot].nxt = head[u]; head[u] = tot++;
}

void dfs1(int u, int pre, int d) {
	dep[u] = d; fa[u] = pre; num[u] = 1;
	for (int i = head[u]; i != -1; i = e[i].nxt) {
		int v = e[i].to;
		if (v != pre) {
			dfs1(v, u, d + 1);
			num[u] += num[v];
			if (son[u] == -1 || num[v] > num[son[u]])son[u] = v;
		}
	}
}

void dfs2(int u, int sp) {
	top[u] = sp;
	if (son[u] != -1) {
		p[u] = pos++;
		fp[p[u]] = u;
		dfs2(son[u], sp);
	}
	else {
		p[u] = pos++; fp[p[u]] = u; return;
	}
	for (int i = head[u]; i != -1; i = e[i].nxt) {
		int v = e[i].to;
		if (v != son[u] && v != fa[u])dfs2(v, v);
	}
}

#define lson l,m,rt<<1
#define rson m+1,r,rt<<1|1
int maxx[maxn];
int val[maxn];
void pushup(int rt) {
	maxx[rt] = max(maxx[rt << 1], maxx[rt << 1 | 1]);
}
void build(int l, int r, int rt) {
	if (l == r) {
		maxx[rt] = val[l]; return;
	}
	int m = (l + r) >> 1;
	build(lson); build(rson); pushup(rt);
}
void upd(int p, int x, int l, int r, int rt) {
	if (l == r) {
		maxx[rt] = x; return;
	}
	int m = (l + r) >> 1;
	if (p <= m)upd(p, x, lson);
	else upd(p, x, rson);
	pushup(rt);
}
int query(int L, int R, int l, int r, int rt) {
	if (L <= l && r <= R) {
		return maxx[rt];
	}
	int m = (l + r) >> 1;
	int ans = 0;
	if (L <= m)ans = max(ans, query(L, R, lson));
	if (m < R)ans = max(ans, query(L, R, rson));
	return ans;
}

int Find(int u, int v) {
	int f1 = top[u], f2 = top[v];
	int tmp = 0;
	while (f1 != f2) {
		if (dep[f1] < dep[f2]) {
			swap(f1, f2); swap(u, v);
		}
		tmp = max(tmp, query(p[f1], p[u], 1, n, 1));
		u = fa[f1]; f1 = top[u];
	}
	if (u == v)return tmp;
	if (dep[u] > dep[v])swap(u, v);
	return max(tmp, query(p[son[u]], p[v], 1, n, 1));
}
int ed[maxn][3];

int main()
{
	//	ios::sync_with_stdio(0);
	int t; t = rd();
	while (t--) {
		init(); n = rd();
	//	getchar();
		for (int i = 0; i < n - 1; i++) {
			ed[i][0] = rd(); ed[i][1] = rd(); ed[i][2] = rd();
			addedge(ed[i][0], ed[i][1]);
			addedge(ed[i][1], ed[i][0]);
		}
		dfs1(1, 0, 0); dfs2(1, 1);
		for (int i = 0; i < n - 1; i++) {
			if (dep[ed[i][0]] < dep[ed[i][1]]) {
				swap(ed[i][0], ed[i][1]);
			}
			val[p[ed[i][0]]] = ed[i][2];
		}
		build(1, n, 1);
		char opt[10];
		while (scanf("%s",opt)) {
			if (opt[0] == ‘D‘)break;
			int u, v; u = rd(); v = rd();
			if (opt[0] == ‘Q‘) {
				printf("%d\n", Find(u, v));
			}
			else upd(p[ed[u - 1][0]], v, 1, n, 1);
		}
	}
	return 0;
}