NC201891 采蘑菇的克拉莉丝（树链剖分）

传送门

分析

先处理出重链，再用线段树维护区间和（单点更新）

查询核心代码

LL ans = 0;
for (int i = h[root]; ~i; i = ne[i])//便利当前root所连的所有边
{
	int t = e[i];//与root直接相连的点
    if (t == fa[root])//如果是父节点
    {
    	ans += (query_tree(1) - query_tree(root)) * w[i];
    }
    else//如果是儿子节点
    {
        ans += query_tree(t) * w[i];
    }
}
printf("%lld\n", ans);

代码

#include 

using namespace std;
//-----pre_def----
const double PI = acos(-1.0);
const int INF = 0x3f3f3f3f;
typedef long long LL;
typedef unsigned long long ULL;
typedef pair<int, int> PII;
typedef pair<double, double> PDD;
#define fir(i, a, b) for (int i = (a); i <= (b); i++)
#define rif(i, a, b) for (int i = (a); i >= (b); i--)
#define endl '\n'
#define init_h memset(h, -1, sizeof h), idx = 0;
#define lowbit(x) x &(-x)

//---------------
const int N = 1e6 + 10;
int h[N], e[N << 1], w[N << 1], ne[N << 1], idx;
int n, q, root = 1;
int dep[N], fa[N], sz[N], top[N], son[N], nd[N], cnt;
struct node
{
    int l, r;
    LL v;
} tr[N << 2];

void add(int a, int b, int c)
{
    e[idx] = b;
    w[idx] = c;
    ne[idx] = h[a];
    h[a] = idx++;
}

void dfs1(int u, int father, int depth)
{
    dep[u] = depth, fa[u] = father, sz[u] = 1;
    for (int i = h[u]; ~i; i = ne[i])
    {
        int t = e[i];
        if (t == fa[u])
            continue;
        dfs1(t, u, depth + 1);
        sz[u] += sz[t];
        if (sz[son[u]] < sz[t])
        {
            son[u] = t;
        }
    }
}

void dfs2(int u, int father)
{
    nd[u] = ++cnt;
    top[u] = father;
    if (!son[u])
        return;
    dfs2(son[u], father);
    for (int i = h[u]; ~i; i = ne[i])
    {
        int t = e[i];
        if (t == fa[u] || t == son[u])
            continue;
        dfs2(t, t);
    }
}

void pushup(int u)
{
    tr[u].v = tr[u << 1].v + tr[u << 1 | 1].v;
}

void build(int u, int l, int r)
{
    tr[u] = {l, r, 0};
    if (l == r)
    {
        return;
    }
    int mid = l + r >> 1;
    build(u << 1, l, mid), build(u << 1 | 1, mid + 1, r);
}

void modify(int u, int l, int r, int k)
{
    //cout<
    if (l <= tr[u].l && tr[u].r <= r)
    {
        tr[u].v += k;
        return;
    }
    int mid = tr[u].l + tr[u].r >> 1;
    if (l <= mid)
        modify(u << 1, l, r, k);
    if (mid < r)
        modify(u << 1 | 1, l, r, k);
    pushup(u);
}

LL query(int u, int l, int r)
{
    if (l <= tr[u].l && tr[u].r <= r)
    {
        return tr[u].v;
    }
    LL res = 0;
    int mid = tr[u].l + tr[u].r >> 1;
    if (l <= mid)
        res += query(u << 1, l, r);
    if (mid < r)
        res += query(u << 1 | 1, l, r);
    return res;
}

LL query_tree(int u)
{
    return query(1, nd[u], nd[u] + sz[u] - 1);
}

int main()
{
#ifndef ONLINE_JUDGE
    freopen("in.txt", "r", stdin);
    freopen("out.txt", "w", stdout);
    int StartTime = clock();
#endif
    scanf("%d", &n);
    init_h;
    fir(i, 1, n - 1)
    {
        int a, b, v;
        scanf("%d%d%d", &a, &b, &v);
        add(a, b, v);
        add(b, a, v);
    }
    dfs1(1, -1, 1);
    dfs2(1, 1);
    build(1, 1, n);
    scanf("%d", &q);
    while (q--)
    {
        int op, v, x;
        scanf("%d", &op);
        if (op == 1)
        {
            scanf("%d%d", &v, &x);
            modify(1, nd[v], nd[v], x);
            LL ans = 0;
            for (int i = h[root]; ~i; i = ne[i])
            {
                int t = e[i];
                if (t == fa[root])
                {
                    ans += (query_tree(1) - query_tree(root)) * w[i];
                }
                else
                {
                    ans += query_tree(t) * w[i];
                }
            }
            printf("%lld\n", ans);
        }
        else
        {
            scanf("%d", &v);
            root = v;
            LL ans = 0;
            for (int i = h[root]; ~i; i = ne[i])
            {
                int t = e[i];
                if (t == fa[root])
                {
                    ans += (query_tree(1) - query_tree(root)) * w[i];
                }
                else
                {
                    ans += query_tree(t) * w[i];
                }
            }
            printf("%lld\n", ans);
        }
    }

#ifndef ONLINE_JUDGE
    printf("Run_Time = %d ms\n", clock() - StartTime);
#endif
    return 0;
}