HDU 3966 RE 树链剖分 线段树 Aragorn's Story

题意：

给出一棵树，每个顶点上有一个权值。

操作：选择一条路径，并将路径上所有的点的权值同时加或减某个数。

查询：某个点的当前权值

分析：

树链剖分完毕后，就是简单的线段树区间更新。

提交的时候注意要要加一句扩栈的代码，用C++提交。

#include <cstdio>
#include <cstring>
#include <algorithm>
using namespace std;

void read(int& x) {
    x = 0;
    char c = ' ';
    while(c < '0' || c > '9') c = getchar();
    while('0' <= c && c <= '9') {
        x = x * 10 + c - '0';
        c = getchar();
    }
}

const int maxn = 50000 + 10;
const int maxnode = maxn * 4;

struct Edge
{
    int v, nxt;
    Edge() {}
    Edge(int v, int nxt) :v(v), nxt(nxt) {}
};

int n, m, q;
int a[maxn];

int ecnt, head[maxn];
Edge edges[maxn * 2];

void AddEdge(int u, int v) {
    edges[++ecnt] = Edge(v, head[u]);
    head[u] = ecnt;
    edges[++ecnt] = Edge(u, head[v]);
    head[v] = ecnt;
}

int dep[maxn], fa[maxn], son[maxn], sz[maxn];

int tot, id[maxn], pos[maxn], top[maxn];

void dfs(int u) {
    sz[u] = 1; son[u] = -1;
    for(int i = head[u]; i; i = edges[i].nxt) {
        int v = edges[i].v;
        if(v == fa[u]) continue;
        fa[v] = u;
        dep[v] = dep[u] + 1;
        dfs(v);
        sz[u] += sz[v];
        if(son[u] == -1 || sz[v] > sz[son[u]]) son[u] = v;
    }
}

void dfs2(int u, int tp) {
    top[u] = tp;
    id[u] = ++tot;
    pos[tot] = u;
    if(son[u] == -1) return;
    if(son[u]) dfs2(son[u], tp);
    for(int i = head[u]; i; i = edges[i].nxt) {
        int v = edges[i].v;
        if(v == fa[u] || v == son[u]) continue;
        dfs2(v, v);
    }
}

int sumv[maxnode], addv[maxnode];
char cmd[10];

void pushup(int o) { sumv[o] = sumv[o<<1] + sumv[o<<1|1]; }

void build(int o, int L, int R) {
    if(L == R) { sumv[o] = a[pos[L]]; return; }
    int M = (L + R) / 2;
    build(o<<1, L, M);
    build(o<<1|1, M+1, R);
    pushup(o);
}

void pushdown(int o, int L, int R) {
    if(addv[o]) {
        addv[o<<1] += addv[o];
        addv[o<<1|1] += addv[o];
        int M = (L + R) / 2;
        sumv[o<<1] += (M - L + 1) * addv[o];
        sumv[o<<1|1] += (R - M) * addv[o];
        addv[o] = 0;
    }
}

void update(int o, int L, int R, int qL, int qR, int v) {
    if(qL <= L && R <= qR) {
        sumv[o] += (R - L + 1) * v;
        addv[o] += v;
        return;
    }
    pushdown(o, L, R);
    int M = (L + R) / 2;
    if(qL <= M) update(o<<1, L, M, qL, qR, v);
    if(qR > M) update(o<<1|1, M+1, R, qL, qR, v);
    pushup(o);
}

void UPDATE(int u, int v, int val) {
    int t1 = top[u], t2 = top[v];
    while(t1 != t2) {
        if(dep[t1] < dep[t2]) { swap(u, v); swap(t1, t2); }
        update(1, 1, n, id[t1], id[u], val);
        u = fa[t1]; t1 = top[u];
    }
    if(dep[u] > dep[v]) swap(u, v);
    update(1, 1, n, id[u], id[v], val);
}

int query(int o, int L, int R, int p) {
    if(L == R) return sumv[o];
    pushdown(o, L, R);
    int M = (L + R) / 2;
    if(p <= M) return query(o<<1, L, M, p);
    else return query(o<<1|1, M+1, R, p);
}

int main()
{
    while(scanf("%d%d%d", &n, &m, &q) == 3) {
        for(int i = 1; i <= n; i++) read(a[i]);

        memset(head, 0, sizeof(head));
        ecnt = 0;
        for(int i = 1; i < n; i++) {
            int u, v; read(u); read(v);
            AddEdge(u, v);
        }

        dfs(1);
        tot = 0;
        dfs2(1, 1);

        memset(addv, 0, sizeof(addv));
        build(1, 1, n);

        while(q--) {
            scanf("%s", cmd);
            int u, v, d;
            read(u);
            if(cmd[0] == 'Q') {
                printf("%d
", query(1, 1, n, id[u]));
            } else {
                read(v); read(d);
                if(cmd[0] == 'D') d = -d;
                UPDATE(u, v, d);
            }
        }
    }

    return 0;
}