树链剖分学习

参考代码：

#include <cstdio>
#include <algorithm>
#include <iostream>
#include <vector>
#include <map>
#include <queue>
#include <set>
#include <ctime>
#include <cstring>
#include <cstdlib>
#include <math.h>
using namespace std;
typedef long long ll;
const int N = 1005;
const int maxn = 1e6 + 5;
struct node
{
	int v, nex;
} edge[maxn << 1];
int head[maxn], w[maxn], son[maxn], deep[maxn];
int pre[maxn], sizx[maxn], dfn[maxn], top[maxn], a[maxn];
int cnt, cnx;
void add(int u, int v)
{
	edge[cnt].v = v, edge[cnt].nex = head[u];
	head[u] = cnt++;
}
void dfs1(int u, int fa)
{
	pre[u] = fa;
	deep[u] = deep[fa] + 1;
	sizx[u] = 1;
	int maxson = -1;
	for (int i = head[u]; ~i; i = edge[i].nex)
	{
		int v = edge[i].v;
		if (v != fa)
		{
			dfs1(v, u);
			sizx[u] += sizx[v];
			if (maxson < sizx[v])
			{
				son[u] = v;
				maxson = sizx[v];
			}
		}
	}
}
void dfs2(int u, int t)
{
	top[u] = t;
	dfn[u] = ++cnx;
	a[cnx] = w[u];
	if (!son[u])
		return;
	dfs2(son[u], t);
	for (int i = head[u]; ~i; i = edge[i].nex)
	{
		int v = edge[i].v;
		if (v != pre[u] && v != son[u])
		{
			dfs2(v, v);
		}
	}
}
struct vain
{
	int l, r, p, lazy;
} tr[maxn << 2];
void pushdown(int k)
{
	if (tr[k].lazy)
	{
		tr[k << 1].p += tr[k].lazy;
		tr[k << 1 | 1].p += tr[k].lazy;
		tr[k << 1].lazy += tr[k].lazy;
		tr[k << 1 | 1].lazy += tr[k].lazy;
		tr[k].lazy = 0;
	}
}
void build(int k, int l, int r)
{
	tr[k].l = l, tr[k].r = r, tr[k].lazy = 0;
	if (l == r)
	{
		tr[k].p = a[l];
		return;
	}
	int mid = l + r >> 1;
	build(k << 1, l, mid);
	build(k << 1 | 1, mid + 1, r);
}
void modify(int k, int ql, int qr, int w)
{
	if (tr[k].l >= ql && tr[k].r <= qr)
	{
		tr[k].p += w;
		tr[k].lazy += w;
		return;
	}
	pushdown(k);
	int mid = tr[k].l + tr[k].r >> 1;
	if (ql <= mid)
	{
		modify(k << 1, ql, qr, w);
	}
	if (qr > mid)
	{
		modify(k << 1 | 1, ql, qr, w);
	}
}
int query(int k, int pos)
{
	if (tr[k].l == tr[k].r)
	{
		return tr[k].p;
	}
	pushdown(k);
	int mid = tr[k].l + tr[k].r >> 1;
	if (mid >= pos)
		return query(k << 1, pos);
	else
		return query(k << 1 | 1, pos);
}
void swap(int &x, int &y)
{
	int tep = x;
	x = y, y = tep;
}
void mtre(int x, int y, int z)
{
	while (top[x] != top[y])
	{
		if (deep[top[x]] < deep[top[y]])
			swap(x, y);
		modify(1, dfn[top[x]], dfn[x], z);
		x = pre[top[x]];
	}
	if (deep[x] > deep[y])
		swap(x, y);
	modify(1, dfn[x], dfn[y], z);
}
int main()
{
	ios::sync_with_stdio(false);
	cin.tie(0);
	int n, m, q;
	while (cin >> n >> m >> q)
	{
		memset(son, 0, sizeof son);
		memset(head, -1, sizeof head);
		cnx = cnt = 0;
		int u, v;
		for (int i = 1; i <= n; i++)
			cin >> w[i];
		for (int i = 0; i < m; i++)
		{
			cin >> u >> v;
			add(u, v), add(v, u);
		}
		dfs1(1, 0);
		dfs2(1, 1);
		build(1, 1, n);
		while (q--)
		{
			char c;
			cin >> c;
			if (c == 'I')
			{
				int u, v, w;
				cin >> u >> v >> w;
				mtre(u, v, w);
			}
			if (c == 'D')
			{
				int u, v, w;
				cin >> u >> v >> w;
				mtre(u, v, -w);
			}
			if (c == 'Q')
			{
				int p;
				cin >> p;
				cout << query(1, dfn[p]) << endl;
			}
		}
	}
}