测评记录

#include <iostream>
#include <algorithm>
using namespace std;

#define MOD p
#define MAX 200001
#define INF 0x7fffffff

int n, m, r, p, w[MAX], opt, x, y, z;
int fa[MAX], dep[MAX], size[MAX], son[MAX];
//节点的: 父亲 深度 子树的节点个数 重儿子
int top[MAX], dfn[MAX], rank[MAX], cnt = 0, wt[MAX];
//节点的: 所在重链顶部节点 Dfs序 Dfs序对应节点编号 cnt 点权

//链式前向星
struct Edge {
    int to, next;
} e[MAX];
int head[MAX], num = 0;
void add(int u, int v) {
    e[++num].to = v;
    e[num].next = head[u];
    head[u] = num;
}

//Dfs
void Dfs1(int u, int f, int deep) {
    fa[u] = f;
    dep[u] = deep;
    size[u] = 1;
    int maxson = -INF;
    for (int i = head[u]; i != 0; i = e[i].next) {
        int v = e[i].to;
        if (v == f)
            continue;
        Dfs1(v, u, deep + 1);
        size[u] += size[v];
        if (size[v] > maxson) {
            son[x] = v;
            maxson = size[v];
        }
    }
}
void Dfs2(int u, int topf) {
    dfn[u] = ++cnt;
    wt[cnt] = w[u];
    top[u] = topf;
    if (!son[u])
        return;
    Dfs2(son[u], topf);
    for (int i = head[u]; i != 0; i = e[i].next) {
        int v = e[i].to;
        if (v == fa[u] || v == son[u])
            continue;
        Dfs2(v, v);
    }
}

//线段树
int tree[MAX << 2], lazy[MAX << 2];
void Build(int rt, int l, int r) {
    if (l == r) {
        tree[rt] = wt[l];
        return;
    }
    int mid = (l + r) >> 1;
    Build(rt << 1, l, mid);
    Build(rt << 1 | 1, mid + 1, r);
    tree[rt] = tree[rt << 1] + tree[rt << 1 | 1];
    tree[rt] %= MOD;
}
void Update(int rt, int l, int r, int w) {
    tree[rt] += (r - l + 1) * w % MOD;
    lazy[rt] += w %= MOD;
} 
void Pushdown(int rt, int l, int r) {
    int mid = (l + r) >> 1;
    Update(rt << 1, l, mid, lazy[rt]);
    Update(rt << 1 | 1, mid + 1, r, lazy[rt]);
    lazy[rt] = 0;
}
void Modify(int rt, int l, int r, int s, int t, int w) {
    if (s <= l && r <= t) {
        Update(rt, l, r, w);
        return;
    }
    Pushdown(rt, l, r);
    int mid = (l + r) >> 1;
    if (s <= mid)
        Modify(rt << 1, l, mid, s, t, w);
    if (t > mid)
        Modify(rt << 1 | 1, mid + 1, r, s, t, w);
    tree[rt] = tree[rt << 1] + tree[rt << 1 | 1];
    tree[rt] %= MOD;
}
int Query(int rt, int l, int r, int s, int t) {
    if (s <= l && r <= t)
        return tree[rt] % MOD;
    Pushdown(rt, l, r);
    int mid = (l + r) >> 1;
    int lson = Query(rt << 1, l, mid, s, t) % MOD;
    int rson = Query(rt << 1 | 1, mid + 1, r, s, t) % MOD;
    if (t <= mid)
        return lson;
    else if (s > mid)
        return rson;
    else
        return lson + rson;
}

//Mode
void Mrange(int x, int y, int z) {
    z %= MOD;
    while (top[x] != top[y]) {
        if (dep[top[x]] < dep[top[y]])
            swap(x, y);
        Modify(1, 1, n, dfn[top[x]], dfn[x], z);
        x = fa[top[x]];
    }
    if (dep[x] > dep[y])
        swap(x, y);
    Modify (1, 1, n, dfn[x], dfn[y], z);
}
int Qrange(int x, int y) {
    int ans = 0;
    while (top[x] != top[y]) {
		if (dep[top[x]] < dep[top[y]])
            swap(x, y);
		ans += Query(1, 1, n, dfn[top[x]], dfn[x]);
		ans %= MOD;
		x = fa[top[x]];
	}
	if(dep[x] > dep[y])
        swap(x, y);
	ans += Query(1, 1, n, dfn[x], dfn[y]);
	ans %= MOD;
	return ans;
}
void Mtree(int x, int z) {
    Modify(1, 1, n, dfn[x], dfn[x]+size[x]-1, z);
}
int Qtree(int x) {
    return Query(1, 1, n, dfn[x], dfn[x] + size[x] - 1);
}

int main() {
    cin >> n >> m >> r >> p;
    for (int i = 1; i <= n; i++)
        cin >> w[i];
    for (int i = 1; i < n; i++) {
        cin >> x >> y;
        add(x, y);
        add(y, x);
    }
    Dfs1(r, 0, 1);
    Dfs2(r, r);
    Build(1, 1, n);
    while (m--) {
        cin >> opt;
        switch (opt) {
            case 1:
                cin >> x >> y >> z;
                Mrange(x, y, z);
                break;
            case 2:
                cin >> x >> y;
                cout << Qrange(x, y) << "\n";
                break;
            case 3:
                cin >> x >> z;
                Mtree(x, z);
                break;
            case 4:
                cin >> x;
                cout << Qtree(x) << "\n";
                break;
            default:
                break;
        }
    }

    return 0;
}

感谢大家！灌水区一个正经的都没有: (