HYSBZ - 2243

vjudge上已经关闭了，要去洛谷提交才行。
板子题目，注意线段树查询的时候，被分段了，也要去判断颜色。在这里wa了一发。

#include<iostream>
#include<cstring>
#include<algorithm>
#include<cmath>
#include<cstdlib>
#include<climits>
#include<stack>
#include<vector>
#include<queue>
#include<set>
#include<map>
//#include<regex>
#include<cstdio>
#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;
const double esp = 1e-6;
const double pi = acos(-1.0);
const int INF = 0x3f3f3f3f;
const int inf = 1e9;
using namespace std;
ll read()
{
	char ch = getchar(); ll 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 = 1e5 + 10;
struct node { int to, next; }edge[2*N];
int head[N];
int id[N], rk[N], son[N], fa[N], siz[N], dep[N], top[N], wi[N];
int n, m;
struct Tree { int lcol, rcol, sum; }tree[N<<2];
int lazy[N << 2];
int cnt = 0;
int num = 0;
void addedge(int u, int v)
{
	edge[cnt].to = v;
	edge[cnt].next = head[u];
	head[u] = cnt++;
}
void pushup(int root)
{
	tree[root].sum = tree[lrt].sum + tree[rrt].sum;
	if (tree[lrt].rcol == tree[rrt].lcol)tree[root].sum--;
	tree[root].lcol = tree[lrt].lcol;
	tree[root].rcol = tree[rrt].rcol;
}
void pushdown(int root)
{
	if (lazy[root] != -1)
	{
		lazy[lrt] = lazy[rrt] = lazy[root];
		tree[lrt].lcol = tree[lrt].rcol = lazy[root];
		tree[rrt].lcol = tree[rrt].rcol = lazy[root];
		tree[lrt].sum = tree[rrt].sum = 1;
		lazy[root] = -1;
	}
}
void build(int l, int r, int root)
{
	lazy[root] = -1;
	if (l == r) {
		tree[root].lcol = tree[root].rcol = wi[rk[l]];
		tree[root].sum = 1;
		return;
	}
	int mid = (l + r) >> 1;
	build(lson); build(rson);
	pushup(root);
}
void update(int l, int r, int root, int lf, int rt, int c)
{
	if (lf <= l && r <= rt)
	{
		tree[root].sum = 1;
		tree[root].lcol = tree[root].rcol = c;
		lazy[root] = c;
		return;
	}
	pushdown(root);
	int mid = (l + r) >> 1;
	if (lf <= mid)update(lson, lf, rt, c);
	if (rt > mid)update(rson, lf, rt, c);
	pushup(root);
}
int querry(int l, int r, int root, int lf, int rt)
{
	if (lf <= l && r <= rt)
	{
		return tree[root].sum;
	}
	pushdown(root);
	int mid = (l + r) >> 1;
	int ans = 0;
	bool left=0;
	if (lf <= mid)ans += querry(lson, lf, rt), left = 1;
	if (rt > mid) {
		ans += querry(rson, lf, rt); 
		if (left)
		{
			if (tree[lrt].rcol == tree[rrt].lcol)ans--;
		}
	}
	return ans;
}
int querrycol(int l, int r, int root, int pos)
{
	if (l == r)
	{
		return tree[root].lcol;
	}
	pushdown(root);
	int mid = (l + r) >> 1;
	if (pos <= mid)return querrycol(lson, pos);
	else return querrycol(rson, pos);
}
void dfs1(int u, int f, int d)
{
	fa[u] = f;
	dep[u] = d;
	siz[u] = 1;
	for (int i = head[u]; ~i; i = edge[i].next)
	{
		int v = edge[i].to;
		if (v == f)continue;
		dfs1(v, u, d + 1);
		siz[u] += siz[v];
		if (son[u] == -1 || siz[son[u]] < siz[v])
		{
			son[u] = v;
		}
	}
}
void dfs2(int u, int tp)
{
	id[u] = ++num;
	rk[num] = u;
	top[u] = tp;
	if (son[u] == -1)return;
	dfs2(son[u], tp);
	for (int i = head[u]; ~i; i = edge[i].next)
	{
		int v = edge[i].to;
		if (v == fa[u]|| v == son[u])continue;
		dfs2(v, v);
	}
}
void rgupdate(int x, int y,int c)
{
	while (top[x] != top[y])
	{
		if (dep[top[x]] < dep[top[y]])swap(x, y);
		update(1, n, 1, id[top[x]], id[x], c);
		x = fa[top[x]];
	}
	if (dep[x] < dep[y])swap(x, y);
	update(1, n, 1, id[y], id[x], c);
}
int rgquerry(int x, int y)
{
	int ans = 0;
	while (top[x] != top[y])
	{
		if (dep[top[x]] < dep[top[y]])swap(x, y);
		ans += querry(1, n, 1, id[top[x]], id[x]);
		if (querrycol(1,n,1,id[top[x]])==querrycol(1,n,1,id[fa[top[x]]]))ans--;
		x = fa[top[x]];
	}
	if (dep[x] < dep[y])swap(x, y);
	ans += querry(1, n, 1, id[y], id[x]);
	return ans;
}
int main()
{
	n = read(), m = read();
	memset(head, -1, sizeof(head));
	memset(son, -1, sizeof(son));
	upd(i, 1, n)wi[i] = read();
	int u, v;
	upd(i, 1, n-1) {
		u = read(), v = read();
		addedge(u, v); addedge(v, u);
	}
	dfs1(1, 0, 1);
	dfs2(1, 1);
	build(1, n, 1);
	char op[2];
	int c;
	while (m--)
	{
		cin >> op;
		if (op[0] == 'C')
		{
			u = read(), v = read(); c = read();
			rgupdate(u, v, c);
		}
		else
		{
			u = read(), v = read();
			int temp = rgquerry(u, v);
			printf("%d\n", temp);
		}
	}
	return 0;
}