自闭了, 真的搞不懂split之后cut和Link的操作, 但感觉不是那个问题

#include <bits/stdc++.h>
#define mod 51061
#define int long long
#define maxn 200005
using namespace std;
int ch[maxn][2], ans[maxn], sz[maxn], taga[maxn], tagm[maxn], rev[maxn], val[maxn], fa[maxn], n, q;
bool get(int x) {
	return x == ch[fa[x]][1];
}
bool isroot(int x) {
	return (x != ch[fa[x]][0] && x != ch[fa[x]][1]);
}
void pushup(int x) {
	ans[x] = ans[ch[x][0]] + ans[ch[x][1]] + val[x];
	ans[x] %= mod;
	sz[x] = sz[ch[x][0]] + sz[ch[x][1]] + 1;
}
void add(int x, int k) {
	ans[x] += k * sz[x], taga[x] += k, val[x] += k;
	ans[x] %= mod, taga[x] %= mod, val[x] %= mod;
}
void mul(int x, int k) {
	ans[x] *= k, taga[x] *= k, tagm[x] *= k, val[x] *= k;
	ans[x] %= mod, taga[x] %= mod, tagm[x] %= mod, val[x] %= mod;
}
void rotate(int x) {
	int y = fa[x], z = fa[y], chk = get(x);
	if(!isroot(y)) ch[z][get(y)] = x;
	ch[y][chk] = ch[x][chk ^ 1], fa[ch[x][chk ^ 1]] = y;
	ch[x][chk ^ 1] = y;
	fa[y] = x, fa[x] = z;
	pushup(y), pushup(x);
}
void pushv(int p) {
	swap(ch[p][0], ch[p][1]);
	rev[p] ^= 1;
}
void pushdown(int x) {
	if(rev[x]) {
		if(ch[x][0]) pushv(ch[x][0]);
		if(ch[x][1]) pushv(ch[x][1]);
		rev[x] = 0;
	}
	if(taga[x]) {
		if(ch[x][0]) add(ch[x][0], taga[x]);
		if(ch[x][1]) add(ch[x][1], taga[x]);
		taga[x] = 0;
	}
	if(tagm[x] != 1) {
		if(ch[x][0]) mul(ch[x][0], tagm[x]);
		if(ch[x][1]) mul(ch[x][1], tagm[x]);
		tagm[x] = 1;
	}
}
void update(int x) {
	if(fa[x]) update(fa[x]);
	pushdown(x);
}
void splay(int x) {
	update(x);
	for(int f = 0;f = fa[x], !isroot(x);rotate(x)) {
		if(!isroot(f)) rotate(get(x) == get(f) ? f : x);
	}
}
void access(int x) {
	for(int f = 0;x;x = fa[f = x]) {
		splay(x), ch[x][1] = f, pushup(x);
		
	}	
}
void makeroot(int x) {
	access(x), splay(x), pushv(x);
}
void split(int x, int y) {
	makeroot(x), access(y), splay(y);
} 
int find(int p) {
	access(p), splay(p);
	while(ch[p][0]) p = ch[p][0];
	splay(p);
	return p;
}
void link(int x, int y) {  
	split(x, y);
	/*if(find(x) != find(y)) */fa[x] = y;
}
void cut(int x, int y) {
	split(x, y);
//	if(find(y) == find(x) && fa[y] == x && !ch[x][0]) { 
		fa[x] = ch[y][0] = 0;
//		pushup(x);
//	}
}

signed main() {
//	freopen("q.in", "r", stdin);
//	freopen("w.out", "w", stdout);
	scanf("%lld%lld", &n, &q);
	for(int i = 1;i <= n;i++) tagm[i] = val[i] = sz[i] = 1;
	for(int i = 1;i <= n - 1;i++) {
		int u, v;
		scanf("%lld%lld", &u, &v);
		link(u, v);
	}
	for(int i = 1;i <= q;i++) {
		char p;
		int x, y, z, k;
		cin >> p;scanf("%lld%lld", &x, &y);
		if(p == '+') {
			scanf("%lld", &z);
			split(x, y);
			add(y, z);
//			cout << ans[y] << endl;
		}
		else if(p == '-') {
			scanf("%lld%lld", &k, &z);
			cut(x, y);
			link(z, k);
		}
		else if(p == '*') {
			scanf("%lld", &z);
			split(x, y);
			mul(y, z);
		}
		else {
			split(x, y);
			printf("%lld\n", ans[y]);
		}
	}
}