P2590 [ZJOI2008]树的统计 - 树剖

我写线段树的时候因为不想用define所以先写好一行
int ls = w * 2, rs = w * 2 + 1, mid = (l + r) / 2;
然后复制下来，每次用的时候粘贴。。。
注意输入的值有负数，求最值的时候注意点。。。

#include <algorithm>
#include <iostream>
#include <cstring>
#include <cstdio>
#include <queue>
using namespace std;
#define debug(x) cerr << #x << "=" << x << endl;
const int MAXN = 30000 + 10;
const int MAXM = MAXN * 2;
const int INF = 1 << 30;
typedef long long ll;
int n,q,hld_cnt,dep[MAXN],fa[MAXN],last[MAXN],siz[MAXN],dfn[MAXN],rnk[MAXN],val[MAXN];
int edge_tot,top[MAXN],son[MAXN];

struct Edge{
	int u, v, to;
	Edge(){}
	Edge(int u, int v, int to) : u(u), v(v), to(to) {}
}e[MAXM];

inline void add(int u, int v) {
	e[++edge_tot] = Edge(u, v, last[u]);
	last[u] = edge_tot;
}

//Segment_Tree

struct segment{
	int sum, m;
}tr[MAXN * 4];

void update(int w) {
	tr[w].sum = tr[w*2].sum + tr[w*2+1].sum;
	tr[w].m = max(tr[w*2].m, tr[w*2+1].m);
}

void build(int w, int l, int r) {
	if(l == r) {
		tr[w].sum = tr[w].m = val[rnk[l]];
		return;
	}
	int le = w * 2, ri = w * 2 + 1, mid = (l + r) / 2;
	build(le, l, mid);
	build(ri, mid+1, r);
	update(w);
}

void poi_change(int w, int l, int r, int x, int k) {
	if(l == r) {
		tr[w].sum = k;
		tr[w].m = k;
		return;
	}
	int le = w * 2, ri = w * 2 + 1, mid = (l + r) / 2;
	if(x <= mid) poi_change(le, l, mid, x, k);
	else poi_change(ri, mid+1, r, x, k);
	update(w);
}

int sum_query(int w, int l, int r, int x, int y) {
	int sum = 0;	
	if(x <= l && r <= y) {
		return tr[w].sum;
	}
	int le = w * 2, ri = w * 2 + 1, mid = (l + r) / 2;
	if(x <= mid) sum += sum_query(le, l, mid, x, y);
	if(y > mid) sum += sum_query(ri, mid+1, r, x, y);
	return sum;
}

int max_query(int w, int l, int r, int x, int y) {
	int rmq = -INF;
	if(x <= l && r <= y) {
		return tr[w].m;
	}
	int le = w * 2, ri = w * 2 + 1, mid = (l + r) / 2;
	if(x <= mid) rmq = max(rmq, max_query(le, l, mid, x, y));
	if(y > mid) rmq = max(rmq, max_query(ri, mid+1, r, x, y));
	return rmq;
}

// Heavy_Light_decomposition

void dfs_init(int x, int f, int depth) {
	dep[x] = depth;
	siz[x] = 1;
	fa[x] = f;
	for(int i=last[x]; i; i=e[i].to) {
		int v = e[i].v;
		if(v == f) continue;
		dfs_init(v, x, depth+1);
		if(siz[v] > siz[son[x]]) son[x] = v;
		siz[x] += siz[v];
	}
}

void dfs_top(int x, int t) {
	top[x] = t;
	dfn[x] = ++hld_cnt;
	rnk[hld_cnt] = x;
	if(son[x]) dfs_top(son[x], t);
	for(int i=last[x]; i; i=e[i].to) {
		int v = e[i].v;
		if(v == fa[x] || v == son[x]) continue;
		dfs_top(v, v);
	}
}

void hld_init() {
	dfs_init(1, 0, 1);
	dfs_top(1, 1);
}

int path_max_query(int s, int t) {
	int rmq = -INF;
	while(top[s] != top[t]) {
		if(dep[top[s]] < dep[top[t]]) swap(s, t);
		rmq = max(rmq, max_query(1, 1, n, dfn[top[s]], dfn[s]));
		s = fa[top[s]];
	}
	if(dfn[s] > dfn[t]) swap(s, t);
	rmq = max(rmq, max_query(1, 1, n, dfn[s], dfn[t]));
	return rmq;
}

int path_sum_query(int s, int t) {
	int sum = 0;
	while(top[s] != top[t]) {
		if(dep[top[s]] < dep[top[t]]) swap(s, t);
		sum += sum_query(1, 1, n, dfn[top[s]], dfn[s]);
		s = fa[top[s]];
	}
	if(dfn[s] > dfn[t]) swap(s, t);
	sum += sum_query(1, 1, n, dfn[s], dfn[t]);
	return sum;
}

int main() {
	scanf("%d", &n);
	for(int i=1; i<n; i++) {
		int ai, bi;
		scanf("%d%d", &ai, &bi);
		add(ai, bi);
		add(bi, ai);
	}
	for(int i=1; i<=n; i++) {
		scanf("%d", &val[i]);
	}
	hld_init();
	build(1, 1, n);
	scanf("%d", &q);
	char cmd[10];
	for(int i=1; i<=q; i++) {
		scanf("%s", cmd);
		int u, v, t;
		scanf("%d", &u);
		if(cmd[0] == 'C') {
			scanf("%d", &t);
			poi_change(1, 1, n, dfn[u], t);
		} else if(cmd[1] == 'M') {
			scanf("%d", &v);
			printf("%d\n", path_max_query(u, v));
		} else if(cmd[1] == 'S') {
			scanf("%d", &v);
			printf("%d\n", path_sum_query(u, v));
		}
	}
	return 0;
}