写了两份。

#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 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;
vector<int> g[N];
int fa[N], cnt, siz[N], son[N], dep[N], top[N], val[N], now[N], dfn[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) {
	dfn[u] = ++cnt;
	now[cnt] = u;
	top[u] = f;
	if (son[u]) dfs2(son[u], f);
	else return ;
	for (int i : g[u]) if (i ^ fa[u] && i ^ son[u]) {
		dfs2(i, i);
	}
}
struct SegTree {
	#define ls (k << 1)
	#define rs (k << 1 | 1)
	#define mid ((l + r) >> 1)
	int t[N << 2], lzy[N << 2];
	void build(int k, int l, int r) {
		if (l == r) {
			t[k] = val[now[l]];
			return ;
		}
		build(ls, l, mid); build(rs, mid+1, r);
		t[k] = min(t[ls], t[rs]);
	}
	void pushdown(int k) {
		if (lzy[k]) {
			t[ls] = lzy[ls] = t[rs] = lzy[rs] = lzy[k];
			lzy[k] = 0;
		}
	}
	void modify(int k, int l, int r, int L, int R, int s) {
		if (L <= l && r <= R) {
			t[k] = lzy[k] = s;
			return ;
		}
		pushdown(k);
		if (L <= mid) modify(ls, l, mid, L, R, s);
		if (R > mid) modify(rs, mid+1, r, L, R, s);
		t[k] = min(t[ls], t[rs]);
	}
	int query(int k, int l, int r, int L, int R) {
		if (L <= l && r <= R) return t[k];
		pushdown(k);
		int ans = 2147483647;
		if (L <= mid) smin(ans, query(ls, l, mid, L, R));
		if (R > mid) smin(ans, query(rs, mid+1, r, L, R));
		return ans;
	}
} seg;
void solve() {
	int n, m, s;
	read(n, m);
	for (int i = 1, x, y; i < n; ++i) {
		read(x, y);
		g[x].eb(y); g[y].eb(x);
	} for (int i = 1; i <= n; ++i) read(val[i]);
	read(s); dfs(s, 0); dfs2(s, s);
	seg.build(1, 1, n);
	while (m--) {
		int op, x, y, v;
		read(op);
		if (op == 1) s = read();
		else if (op == 2) {
			read(x, y, v);
			while (top[x] != top[y]) {
				if (dep[top[x]] > dep[top[y]]) swap(x, y);
				seg.modify(1, 1, n, dfn[top[y]], dfn[y], v);
				y = fa[top[y]];
			}
			if (dep[x] > dep[y]) swap(x, y);
			seg.modify(1, 1, n, dfn[x], dfn[y], v);
		} else {
			v = read();
			if (s == v) write(seg.query(1, 1, n, 1, n), '\n');
			else if (dfn[s] >= dfn[v] && dfn[s] < dfn[v] + siz[v]) {
				int ans = 2147483647, L, R;
				if (top[s] != top[v]) {
					while (top[fa[top[s]]] != top[v]) s = fa[top[s]];
					s = top[s];
					L = dfn[s], R = dfn[s] + siz[s] - 1;
				} else L = dfn[v] + 1, R = dfn[v] + siz[son[s]];
				if (L != 1) smin(ans, seg.query(1, 1, n, 1, L-1));
				if (R != n) smin(ans, seg.query(1, 1, n, R+1, n));
				write(ans, '\n');
			} else write(seg.query(1, 1, n, dfn[v], dfn[v] + siz[v] - 1), '\n');
		}
	}
}
signed main() {
	int T = 1;
	// T = read();
	while (T--) solve();
	return 0;
}

和

#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 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;
vector<long long> g[N], sum[N];
int fa[N], cnt, siz[N], son[N], dep[N], top[N], val[N], now[N], dfn[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) {
	dfn[u] = ++cnt;
	now[cnt] = u;
	top[u] = f;
	if (son[u]) dfs2(son[u], f);
	else return ;
	sum[u].eb(1); sum[u].eb(siz[son[u]] + 1);
	for (int i : g[u]) if (i ^ fa[u] && i ^ son[u]) {
		sum[u].eb(siz[i] + sum[u].back());
		dfs2(i, i);
	}
}
struct SegTree {
	#define ls (k << 1)
	#define rs (k << 1 | 1)
	#define mid ((l + r) >> 1)
	int t[N << 2], lzy[N << 2];
	void build(int k, int l, int r) {
		if (l == r) {
			t[k] = val[now[l]];
			return ;
		}
		build(ls, l, mid); build(rs, mid+1, r);
		t[k] = min(t[ls], t[rs]);
	}
	void pushdown(int k) {
		if (lzy[k]) {
			t[ls] = lzy[ls] = t[rs] = lzy[rs] = lzy[k];
			lzy[k] = 0;
		}
	}
	void modify(int k, int l, int r, int L, int R, int s) {
		if (L <= l && r <= R) {
			t[k] = lzy[k] = s;
			return ;
		}
		pushdown(k);
		if (L <= mid) modify(ls, l, mid, L, R, s);
		if (R > mid) modify(rs, mid+1, r, L, R, s);
		t[k] = min(t[ls], t[rs]);
	}
	int query(int k, int l, int r, int L, int R) {
		if (L <= l && r <= R) return t[k];
		pushdown(k);
		int ans = 2147483647;
		if (L <= mid) smin(ans, query(ls, l, mid, L, R));
		if (R > mid) smin(ans, query(rs, mid+1, r, L, R));
		return ans;
	}
} seg;
void solve() {
	int n, m, s;
	read(n, m);
	for (int i = 1, x, y; i < n; ++i) {
		read(x, y);
		g[x].eb(y); g[y].eb(x);
	} for (int i = 1; i <= n; ++i) read(val[i]);
	read(s); dfs(s, 0); dfs2(s, s);
	seg.build(1, 1, n);
	while (m--) {
		int op, x, y, v;
		read(op);
		if (op == 1) s = read();
		else if (op == 2) {
			read(x, y, v);
			while (top[x] != top[y]) {
				if (dep[top[x]] > dep[top[y]]) swap(x, y);
				seg.modify(1, 1, n, dfn[top[y]], dfn[y], v);
				y = fa[top[y]];
			}
			if (dep[x] > dep[y]) swap(x, y);
			seg.modify(1, 1, n, dfn[x], dfn[y], v);
		} else {
			v = read();
			if (s == v) write(seg.query(1, 1, n, 1, n), '\n');
			else if (dfn[s] >= dfn[v] && dfn[s] < dfn[v] + siz[v]) {
				int ans = 2147483647;
				int u = lower_bound(sum[v].begin(), sum[v].end(), dfn[s] - dfn[v]) - sum[v].begin();
				int L = sum[v][u] + dfn[v], R = sum[v][u+1] + dfn[v] - 1;
				if (L != 1) smin(ans, seg.query(1, 1, n, 1, L-1));
				if (R != n) smin(ans, seg.query(1, 1, n, R+1, n));
				write(ans, '\n');
			} else write(seg.query(1, 1, n, dfn[v], dfn[v] + siz[v] - 1), '\n');
		}
	}
}
signed main() {
	int T = 1;
	// T = read();
	while (T--) solve();
	return 0;
}