代码如下，其他地方已调过，应该是树状数组有问题，但我不知道哪里有问题啊啊啊啊。

大佬帮帮忙，孩子已经调了一下午了。

#include <bits/stdc++.h>

using namespace std;

const int N = 1e5 + 10;

int n, m, r, p, cnt;
int t1[N], t2[N];
int dep[N], son[N], dfn[N], fa[N], siz[N], top[N], w[N];

vector<int> g[N];

int L(int x) {
	return x & (-x);
} 

void A(int x, int k) {
	int k1 = (x - 1) * k % p;
	for (; x <= n; x += L(x)) {
		t1[x] = ((t1[x] + k) % p + p) % p;
		t2[x] = ((t2[x] + k1) % p + p) % p;
	}
}

void add(int l, int r, int k) {
	A(l, k), A(r + 1, -k);
}

int Q(int x) {
	int ans = 0;
	for (int o = x; o > 0; o -= L(o)) {
		ans = (ans + x * t1[o] % p) % p;
		ans = (ans - t2[o]) % p;
		ans = (ans + p) % p;
	}
	return ans;
}

int query(int l, int r) {
	return ((Q(r) - Q(l - 1)) % p + p) % p;
}

void dfs1(int u, int f) {
	fa[u] = f;
	siz[u] = 1;
	dep[u] = dep[f] + 1;
	son[u] = 0;
	int sz = g[u].size();
	for (int i = 0; i < g[u].size(); ++i) {
		int v = g[u][i];
		if (v == f) continue;
		dfs1(v, u);
		siz[u] += siz[v];
		if (siz[v] > siz[son[u]]) {
			son[u] = v;
		}
	}
}

void dfs2(int u, int t) {
	top[u] = t;
	dfn[u] = ++cnt;
	if (w[u]) add(dfn[u], dfn[u], w[u]);
	if (!son[u]) return;
	dfs2(son[u], t);
	int sz = g[u].size();
	for (int i = 0; i < sz; ++i) {
		int v = g[u][i];
		if (v != son[u] && v != fa[u]) dfs2(v, v);
	}
}

void addP(int x, int y, int k) {
	while (top[x] != top[y]) {
		if (dep[top[x]] < dep[top[y]]) swap(x, y);
		add(dfn[top[x]], dfn[x], k);
		x = fa[top[x]];
	}
	if (dep[x] > dep[y]) swap(x, y);
	add(dfn[x], dfn[y], k);
}

int queryP(int x, int y) {
	int ans = 0;
	while (top[x] != top[y]) {
		if (dep[top[x]] < dep[top[y]]) swap(x, y);
		ans = (ans + query(dfn[top[x]], dfn[x])) % p;
		x = fa[top[x]];
	}
	if (dep[x] > dep[y]) swap(x, y);
	ans = (ans + query(dfn[x], dfn[y])) % p;
	return ans;
} 

void addS(int x, int k) {
	k %= p;
	add(dfn[x], dfn[x] + siz[x] - 1, k);
}

int queryS(int u) {
	return query(dfn[u], dfn[u] + siz[u] - 1);
}

int main() {
	scanf("%d %d %d %d", &n, &m, &r, &p);
	for (int i = 1; i <= n; ++i) scanf("%d", &w[i]);
	for (int i = 1, u, v; i < n; ++i) {
		scanf("%d %d", &u, &v);
		g[u].push_back(v);
		g[v].push_back(u);
	}
	dfs1(r, 0);
	dfs2(r, r);
	//for (int i = 1; i <= n; ++i) printf("%d ", dfn[i]);
	//puts("");
	for (int i = 1; i <= n; ++i) printf("%d ", t1[i]);
	puts("");
	for (int i = 1; i <= n; ++i) printf("%d ", t2[i]);
	for (int i = 1, opt, x, y, z; i <= m; ++i) {
		scanf("%d", &opt);
		if (opt == 1) {
			scanf("%d %d %d", &x, &y, &z);
			addP(x, y, z);
		}
		if (opt == 2) {
			scanf("%d %d", &x, &y);
			printf("%d\n", queryP(x, y) % p);
		}
		if (opt == 3) {
			scanf("%d %d", &x, &z);
			addS(x, z);
		}
		if (opt == 4) {
			scanf("%d", &x);
			printf("%d\n", queryS(x) % p);
		}
	}
	return 0;
}