树链剖分基础题

#include <cstdio>
#include <cstring>
#include <algorithm>
using namespace std;
const int maxn = 10010;
struct edge
{
	int v, next;
}e[maxn*2];
int first[maxn], cnt;

int top[maxn], dep[maxn], sz[maxn], f[maxn], son[maxn], rank[maxn], tid[maxn];
int tp, tim;
int d[maxn][3];
int n;
void AddEdge(int u, int v)
{
	e[cnt].v = v;
	e[cnt].next = first[u];
	first[u] = cnt++;
	
	e[cnt].v = u;
	e[cnt].next = first[v];
	first[v] = cnt++;
	
}
void init()
{
	memset(first, -1, sizeof(first));
	cnt = 1;
	memset(son, -1, sizeof(son));
	tim = 0;
}

void dfs1(int u, int fa, int d)
{
	sz[u] = 1;
	dep[u] = d;
	f[u] = fa;	
	for(int i = first[u]; i != -1; i = e[i].next)
	{
		int v = e[i].v;
		if(v == fa)
			continue;
		dfs1(v, u, d+1);
		sz[u] += sz[v];
		if(son[u] == -1 || sz[son[u]] < sz[v])
			son[u] = v;
	}
}

void dfs2(int u, int tp)
{
	top[u] = tp;
	tid[u] = ++tim;
	rank[tid[u]] = u;
	if(son[u] == -1)
		return;
	dfs2(son[u], tp);
	for(int i = first[u]; i != -1; i = e[i].next)
	{
		int v = e[i].v;
		if(v != f[u] && son[u] != v)
			dfs2(v, v);
	}
}

int ma[maxn<<2];
int mi[maxn<<2];
int lz[maxn<<2];
void pushup(int l, int r, int rt)
{
	ma[rt] = max(ma[rt<<1], ma[rt<<1|1]);
	mi[rt] = min(mi[rt<<1], mi[rt<<1|1]);
}
void build(int l, int r, int rt)
{	
	ma[rt] = 0;
	mi[rt] = 0;
	lz[rt] = 0;
	if(l == r)
	{
		return;
	}
	int m = (l + r) >> 1;
	build(l, m, rt<<1);
	build(m+1, r, rt<<1|1);
}
void pushdown(int l, int r, int rt)
{
	if(l == r)
		return;
	if(lz[rt])
	{
		mi[rt<<1] = -mi[rt<<1];
		ma[rt<<1] = -ma[rt<<1];
		swap(mi[rt<<1], ma[rt<<1]);
		mi[rt<<1|1] = -mi[rt<<1|1];
		ma[rt<<1|1] = -ma[rt<<1|1];
		swap(mi[rt<<1|1], ma[rt<<1|1]);	
		lz[rt<<1] ^= 1;
		lz[rt<<1|1] ^= 1;
		lz[rt] = 0;
	}
}
void update(int x, int y, int l, int r, int rt)
{
	if(x == l && y == r)
	{
		mi[rt] = -mi[rt];
		ma[rt] = -ma[rt];
		swap(mi[rt], ma[rt]);
		lz[rt] ^= 1;
		return;
	}
	pushdown(l, r, rt);
	int m = (l + r) >> 1;
	if(y <= m)
		update(x, y, l, m, rt<<1);
	else if(x > m)
		update(x, y, m+1, r, rt<<1|1);
	else
	{
		update(x, m, l, m, rt<<1);
		update(m+1, y, m+1, r, rt<<1|1);
	}
	pushup(l, r, rt);
}
void update2(int x, int l, int r, int rt, int w)
{
	if(l == r)
	{
		ma[rt] = mi[rt] = w;
		lz[rt] = 0;
		return;
	}
	pushdown(l, r, rt);
	int m = (l + r) >> 1;
	if(x <= m)
		update2(x, l, m, rt<<1, w);
	else
		update2(x, m+1, r, rt<<1|1, w);
	pushup(l, r, rt);
}
int query(int x, int y, int l, int r, int rt)
{
	if(l == x && r == y)
		return ma[rt];
	pushdown(l, r, rt);
	
	int m = (l + r) >> 1;
	if(y <= m)
		return query(x, y, l, m, rt<<1);
	else if(x > m)
		return query(x, y, m+1, r, rt<<1|1);
	else
	{
		return max(query(x, m, l, m, rt<<1), query(m+1, y, m+1, r, rt<<1|1));
	}
}

void change(int u, int v)
{
	while(top[u] != top[v])
	{
		if(dep[top[u]] < dep[top[v]])
			swap(u, v);
		update(tid[top[u]], tid[u], 1, n, 1);
		u = f[top[u]];
	}
	if(u == v)
		return;
	if(dep[u] > dep[v])
		swap(u, v);
	update(tid[son[u]], tid[v], 1, n, 1);
}
int find(int u, int v)
{
	int ans = -999999999;
	while(top[u] != top[v])
	{
		if(dep[top[u]] < dep[top[v]])
			swap(u, v);
		ans = max(ans, query(tid[top[u]], tid[u], 1, n, 1));
		u = f[top[u]];
	}
	if(u == v)
		return ans;
	if(dep[u] > dep[v])
		swap(u, v);
	ans = max(ans, query(tid[son[u]], tid[v], 1, n, 1));
	return ans;
}
int main()
{
	int T;
	scanf("%d", &T);
	while(T--)
	{
		init();
		
		scanf("%d", &n);
		for(int i = 1; i < n; i++)
		{
			int u, v, w;
			scanf("%d %d %d", &u, &v, &w);
			AddEdge(u, v);
			d[i][0] = u;
			d[i][1] = v;
			d[i][2] = w;
		}
		dfs1(1, 0, 0);
		dfs2(1, 1);
		build(1, n, 1);
		
		for(int i = 1; i < n; i++)
		{
			if(dep[d[i][0]] > dep[d[i][1]])
				swap(d[i][0], d[i][1]);
			update2(tid[d[i][1]], 1, n, 1, d[i][2]);
		}
		char s[10];
		while(scanf("%s", s) && strcmp(s, "DONE"))
		{
			if(s[0] == 'Q')
			{
				int x, y;
				scanf("%d %d", &x, &y);
				printf("%d\n", find(x, y));
			}
			else if(s[0] == 'C')
			{
				int x, y;
				scanf("%d %d", &x, &y);
				update2(tid[d[x][1]], 1, n, 1, y);
			}
			else
			{
				int x, y;
				scanf("%d %d", &x, &y);
				change(x, y);
			}
		}
	} 
	return 0;
}

POJ 3237 Tree 树链剖分