思路大致同第一篇题解。

#include <iostream>
#include <cassert>
#include <queue>
#include <cmath>
#include <cstring>
#include <algorithm>
#include <bitset>
#include <ctime>
#include <map>
#include <set>
using namespace std;
// #define int long long
#define pii pair<int, int>
#define eb emplace_back
#define F first
#define S second
#define test(x) cout << "Test: " << x << '\n'
#define lowbit(x) (x & -x)
#define debug puts("qwq");
#define open(x) freopen(#x".in", "r", stdin);freopen(#x".out", "w", stdout);
#define close fclose(stdin);fclose(stdout);
namespace FastIO {
	template <typename T = int>
	inline T read() {
		T s = 0, w = 1;
		char c = getchar();
		while (!isdigit(c)) {
			if (c == '-') w = -1;
			c = getchar();
		}
		while (isdigit(c)) s = (s << 1) + (s << 3) + (c ^ 48), c = getchar();
		return s * w;
	}
	template <typename T>
	inline void read(T &s) {
		s = 0;
		int w = 1;
		char c = getchar();
		while (!isdigit(c)) {
			if (c == '-') w = -1;
			c = getchar();
		}
		while (isdigit(c)) s = (s << 1) + (s << 3) + (c ^ 48), c = getchar();
		s = s * w;
	}
	template <typename T, typename... Arp> inline void read(T &x, Arp &...arp) {
		read(x), read(arp...);
	}
	template <typename T>
	inline void write(T x, char ch) {
		if (x < 0) x = -x, putchar('-');
		static char stk[25];
		int top = 0;
		do {
			stk[top++] = x % 10 + '0', x /= 10;
		} while (x);
		while (top) putchar(stk[--top]);
		putchar(ch);
		return;
	}
	template <typename T>
	inline void smax(T &x, T y) {
		if (x < y) x = y;
	}
	template <typename T>
	inline void smin(T &x, T y) {
		if (x > y) x = y;
	}
	void quit() {
		exit(0);
	}
} using namespace FastIO;
const int N = 1e5 + 19;
int dfn[N], fa[N], dep[N], top[N], siz[N], son[N], cnt, col[N], u, v, w;
vector<int> g[N];
void dfs(int u, int f) {
	fa[u] = f; dep[u] = dep[f] + 1;
	siz[u] = 1;
	for (int i : g[u]) {
		if (i == f) continue;
		dfs(i, u);
		siz[u] += siz[i];
		if (siz[i] > siz[son[u]]) son[u] = i;
	}
}
void dfs2(int u, int f) {
	top[u] = f; dfn[u] = ++cnt;
	if (son[u]) dfs2(son[u], f);
	for (int i : g[u]) if (i != fa[u] && i != son[u]) dfs2(i, i);
}
struct node { int lc, rc, sum; } t[N << 2];
int tag[N << 2];
node merge(node a, node b) {
	return {a.lc, b.rc, a.sum + b.sum - (a.rc == b.lc)};
}
struct SegTree {
	#define ls (k << 1)
	#define rs (k << 1 | 1)
	#define mid ((l + r) >> 1)
	void pushdown(int k) {
		if (!tag[k]) return ;
		t[ls] = t[rs] = {tag[k], tag[k], 1};
		tag[k] = 0;
	}
	void modify(int k, int l, int r, int L, int R, int u) {
		if (L <= l && r <= R) {
			t[k] = {u, u, 1};
			tag[k] = u;
			return ;
		}
		pushdown(k);
		if (L <= mid) modify(ls, l, mid, L, R, u);
		if (R > mid) modify(rs, mid+1, r, L, R, u);
		t[k] = merge(t[ls], t[rs]);
	}
	node query(int k, int l, int r, int L, int R) {
		if (L <= l && r <= R) return t[k];
		pushdown(k);
		if (L <= mid && R > mid) return merge(query(ls, l, mid, L, R), query(rs, mid+1, r, L, R));
		if (L <= mid) return query(ls, l, mid, L, R);
		return query(rs, mid+1, r, L, R);
	}
} seg;
char G() {
	char c = getchar();
	while (c != 'C' && c != 'Q') c = getchar();
	return c;
}
signed main() {
	int n, q; read(n, q);
	for (int i = 1; i <= n; ++i) read(col[i]);
	for (int i = 1, u, v; i < n; ++i) {
		read(u, v);
		g[u].eb(v); g[v].eb(u);
	} dfs(1, 0); dfs2(1, 1);
	for (int i = 1; i <= n; ++i) seg.modify(1, 1, n, dfn[i], dfn[i], col[i]);
	while (q--) {
		char c = G(); read(u, v);
		if (c == 'C') {
			read(w);
			while (top[u] ^ top[v]) {
				if (dep[top[u]] > dep[top[v]]) {
					swap(u, v);
				} seg.modify(1, 1, n, dfn[top[v]], dfn[v], w);
				v = fa[top[v]];
			}
			if (dep[u] > dep[v]) swap(u, v);
			seg.modify(1, 1, n, dfn[u], dfn[v], w);
		} else {
			node ans1 = {0, 0, 0}, ans2 = {0, 0, 0};
			while (top[u] ^ top[v]) {
				if (dep[top[u]] > dep[top[v]]) {
					ans1 = merge(seg.query(1, 1, n, dfn[top[u]], dfn[u]), ans1);
					u = fa[top[u]];
				} else {
					ans2 = merge(seg.query(1, 1, n, dfn[top[v]], dfn[v]), ans2);
					v = fa[top[v]];
				}
			}
			if (dep[u] > dep[v]) ans1 = merge(seg.query(1, 1, n, dfn[v], dfn[u]), ans1);
			else ans2 = merge(seg.query(1, 1, n, dfn[u], dfn[v]), ans2);
			swap(ans1.lc, ans1.rc);
			write(merge(ans1, ans2).sum, '\n');
		}
	}
	return 0;
}