LightOJ-1348 Aladdin and the Return Journey

Aladdin and the Return Journey

树链剖分模板题

结点单点修改

#include <iostream>
#include <cstdio>
#include <algorithm>
#include <vector>
using namespace std;
const int maxn = 3e4 + 10;
vector<int>gra[maxn];
int dep[maxn];
int siz[maxn];
int hson[maxn];
int fa[maxn];
int top[maxn];
int dfn[maxn];
int rnk[maxn];

int tr[maxn << 2];
int w[maxn];

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

int query(int now, int l, int r, int L, int R)
{
    if(L <= l && r <= R)
        return tr[now];
    int mid = l + r >> 1;
    int ans = 0;
    if(L <= mid)
        ans += query(now << 1, l, mid, L, R);
    if(R > mid)
        ans += query(now << 1 | 1, mid + 1, r, L, R);
    return ans;
}

void update(int now, int l, int r, int x, int val)
{
    if(l == r)
    {
        tr[now] = val;
        return;
    }
    int mid = l + r >> 1;
    if(x <= mid)
        update(now << 1, l, mid, x, val);
    else
        update(now << 1 | 1, mid + 1, r, x, val);
    tr[now] = tr[now << 1] + tr[now << 1 | 1];
}

void dfs1(int now, int pre, int d)
{
    siz[now] = 1;
    hson[now] = -1;
    dep[now] = d;
    fa[now] = pre;
    for(int i=0; i<gra[now].size(); i++)
    {
        int nex = gra[now][i];
        if(nex == fa[now]) continue;
        dfs1(nex, now, d + 1);
        siz[now] += siz[nex];
        if(hson[now] == -1 || siz[hson[now]] < siz[nex])
            hson[now] = nex;
    }
}

int tp = 0;
void dfs2(int now, int t)
{
    top[now] = t;
    tp++;
    dfn[now] = tp;
    rnk[tp] = now;
    if(hson[now] != -1)
    {
        dfs2(hson[now], t);
        for(int i=0; i<gra[now].size(); i++)
        {
            int nex = gra[now][i];
            if(nex == fa[now] || nex == hson[now]) continue;
            dfs2(nex, nex);
        }
    }
}

void init(int n, int rt = 1)
{
    tp = 0;
    dfs1(rt, rt, 1);
    dfs2(rt, rt);
    build(1, 1, n);
    for(int i=0; i<=n; i++) gra[i].clear();
}

int solve(int a, int b, int n)
{
    int ans = 0;
    while(top[a] != top[b])
    {
        if(dep[top[a]] < dep[top[b]]) swap(a, b);
        ans += query(1, 1, n, dfn[top[a]], dfn[a]);
        a = fa[top[a]];
    }
    if(dep[a] > dep[b]) swap(a, b);
    ans += query(1, 1, n, dfn[a], dfn[b]);
    return ans;
}

int main()
{
    int t;
    scanf("%d", &t);
    for(int casee=1; casee<=t; casee++)
    {
        printf("Case %d:\n", casee);
        int n;
        scanf("%d", &n);
        for(int i=0; i<n; i++) scanf("%d", &w[i]);
        for(int i=1; i<n; i++)
        {
            int x, y;
            scanf("%d%d", &x, &y);
            gra[x].push_back(y);
            gra[y].push_back(x);
        }
        init(n, 0);
        int q;
        scanf("%d", &q);
        while(q--)
        {
            int x;
            scanf("%d", &x);
            if(x == 0)
            {
                int i, j;
                scanf("%d%d", &i, &j);
                printf("%d\n", solve(i, j, n));
            }
            else
            {
                int i, v;
                scanf("%d%d", &i, &v);
                update(1, 1, n, dfn[i], v);
            }
        }
    }
    return 0;
}