[Luogu] 魔法树

https://www.luogu.org/problemnew/show/P3833

树链剖分 + 线段树

为啥会RE？？ 不解

#include <iostream>
#include <cstdio>

using namespace std;
const int N = 1e5 + 10;

#define LL long long

int n, T, now = 1, tim;
int top[N], tree[N], lst[N], rst[N], bef[N], size[N], fa[N], deep[N], son[N];
LL W[N << 2], F[N << 2], S[N << 2];
struct Node {int v, nxt;} G[N << 1];
int head[N];
LL Answer;

#define gc getchar()

inline int read() {
    int x = 0; char c = gc;
    while(c < '0' || c > '9') c = gc;
    while(c >= '0' && c <= '9') x = x * 10 + c - '0', c = gc;
    return x;
}

inline void Add(int u, int v) {G[now].v = v; G[now].nxt = head[u]; head[u] = now ++;}

struct Node_1 {
    #define lson jd << 1
    #define rson jd << 1 | 1
    void Build_tree(int l, int r, int jd) {
        S[jd] = r - l + 1;
        if(l == r) return ;
        int mid = (l + r) >> 1;
        Build_tree(l, mid, lson);
        Build_tree(mid + 1, r, rson);
    }
    void Down(int jd) {
        int f = F[jd];
        F[lson] += f; F[rson] += f;
        W[lson] += S[lson] * f; W[rson] += S[rson] * f;
        F[jd] = 0;
    }
    void Sec_G(int l, int r, int jd, int x, int y, int yj) {
        if(x <= l && r <= y) {
            F[jd] += yj; W[jd] += S[jd] * yj; return ;
        }
        if(F[jd]) Down(jd);
        int mid = (l + r) >> 1;
        if(x <= mid) Sec_G(l, mid, lson, x, y, yj);
        if(y > mid ) Sec_G(mid + 1, r, rson, x, y, yj);
        W[jd] = W[lson] + W[rson];
    }
    void Sec_A(int l, int r, int jd, int x, int y) {
        if(x <= l && r <= y) {
            Answer += W[jd]; return ;
        }
        if(F[jd]) Down(jd);
        int mid = (l + r) >> 1;
        if(x <= mid) Sec_A(l, mid, lson, x, y);
        if(y > mid ) Sec_A(mid + 1, r, rson, x, y);
    }
}Seg_tree;

void Dfs_1(int u, int f_, int dep) {
    fa[u] = f_; deep[u] = dep; size[u] = 1;
    for(int i = head[u]; ~ i; i = G[i].nxt) {
        int v = G[i].v;
        if(v != f_) {
            Dfs_1(v, u, dep + 1);
            size[u] += size[v];
            if(size[son[u]] < size[v]) son[u] = v;
        }
    }
}

void Dfs_2(int u, int tp) {
    top[u] = tp;
    tree[u] = ++ tim;
    lst[u] = tim;
    if(!son[u]) {rst[u] = tim; return ;}
    Dfs_2(son[u], tp);
    for(int i = head[u]; ~ i; i = G[i].nxt) {
        int v = G[i].v;
        if(v != fa[u] && v != son[u]) Dfs_2(v, v);
    }
    rst[u] = tim;
}

inline void Sec_G_imp(int x, int y, int w) {
    int tp1 = top[x], tp2 = top[y];
    while(tp1 != tp2) {
        if(deep[tp1] < deep[tp2]) swap(tp1, tp2), swap(x, y);
        Seg_tree.Sec_G(1, n, 1, tree[tp1], tree[x], w);
        x = fa[tp1];
        tp1 = fa[x];
    }
    if(deep[x] < deep[y]) swap(x, y);
    Seg_tree.Sec_G(1, n, 1, tree[y], tree[x], w);
    return ;
}

int main() {
    n = read();
    for(int i = 0; i < n; i ++) son[i] = -1, head[i] = -1;
    for(int i = 1; i < n; i ++) {int u = read(), v = read(); Add(u, v);}
    Seg_tree.Build_tree(1, n, 1);
    Dfs_1(0, 0, 1);
    Dfs_2(0, 0);
    T = read();
    while(T --) {
        string opt; cin >> opt;
        if(opt[0] == 'A') {
            int x = read(), y = read(), w = read();
            Sec_G_imp(x, y, w);    
        } else {
            Answer = 0;
            int x = read();
            Seg_tree.Sec_A(1, n, 1, lst[x], rst[x]);
            cout << Answer << "
";
        }
    }
    
    return 0;
}