Housewife Wind POJ - 2763 (树链剖分）

题目 https://cn.vjudge.net/problem/POJ-2763

题意

求两点间距离

思路

树链剖分

JH https://jhcloud.top/blog/?p=1403

#include <algorithm>
#include <iostream>
#include <cstdio>
#include <cstdlib>
#include <map>
#include <cstring>
#include <vector>
using namespace std;
#define lson o<<1
#define rson o<<1|1
#define MID int m = (l+r)/2

const int maxn =  100001 + 100;
int tree[maxn<<2];

int n,m,p,s;

struct edge
{
    int to,next;
}e[maxn*2];
int son[maxn],top[maxn],tid[maxn]; //重儿子 顶端节点 节点新编号
int siz[maxn],deep[maxn],fa[maxn]; //子树的节点数 深度 父亲节点
int data[maxn];  //节点权值
int id_data[maxn];
int U[maxn],V[maxn],W[maxn];
int _cnt,cnt; //节点编号
int head[maxn];
void add(int u,int v)
{
    e[cnt].to = v;
    e[cnt].next = head[u];
    head[u] = cnt++;
}
void build(int o, int l, int r)
{
    if(l == r)
    {
        tree[o] = id_data[l];
        return ;
    }
    MID;
    build(lson, l, m);
    build(rson, m + 1, r);
    tree[o] = tree[lson] + tree[rson];
}
void updata(int o, int l, int r, int x, int d)
{
    if(l > x || r < x) return ;
    if(l == x && r == x)
    {
        tree[o] = d;
        return ;
    }
    MID;
    updata(lson, l, m, x, d);
    updata(rson, m + 1, r, x, d);
    tree[o] = tree[lson] + tree[rson];
}
int query(int o, int l, int r, int ul, int ur)
{
    if(l > ur || r < ul) return 0;
    if(ul <= l && ur >= r) return tree[o];
    MID;
    return query(lson, l, m, ul, ur) + query(rson, m + 1, r, ul, ur);
}

void dffs(int u, int f, int d) //点 父节点 深度
{
    siz[u] = 1,deep[u] = d;
    fa[u] = f,son[u] = -1;
    for(int i = head[u]; i != -1; i = e[i].next)
    {
        int v = e[i].to;
        if(v != f) //除去父节点
        {
            dffs(v, u, d + 1);
            siz[u] += siz[v];
            if(son[u] == -1||siz[son[u]] < siz[v]) //找重儿子
            {
                son[u] = v;
            }
        }
    }
}
void dfss(int u,int t)
{
    top[u] = t,tid[u] = ++_cnt;
    if(son[u] != -1) dfss(son[u], t); //重儿子
    for(int i = head[u];i!=-1;i = e[i].next)
    {
        int v = e[i].to;
        if(son[u] != v && fa[u] != v) dfss(v,v); //轻儿子
    }
}
int Query(int x, int y) {
    int ans = 0;
    int tx = top[x], ty = top[y];
    while (tx != ty)
    {
        if (deep[tx] < deep[ty]) swap(x, y),swap(tx,ty);
        ans += query(1, 1, n, tid[tx], tid[x]);
        x = fa[tx], tx = top[x];
    }
    if(x == y) return ans;
    if (deep[x] > deep[y]) swap(x, y);
    ans += query(1, 1, n, tid[son[x]], tid[y]);
    return ans;
}

void splite()
{
    _cnt = 0;
    dffs(1, -1, 0);//找重孩子 点信息
    dfss(1, 1); //剖分 （求顶端节点，新编号）
}
void init()
{
    memset(head,-1,sizeof(head));
    cnt = 0;
    for(int i = 1;i < n;i++)
    {
        int u,v,w;
        scanf("%d %d %d", &u, &v, &w);
        add(u,v);
        add(v,u);
        U[i] = u,V[i] = v,W[i] = w;
    }
}
void solve()
{
    splite();//树链剖分
    for(int i=1;i<n;i++)
    {
        if(deep[U[i]]<deep[V[i]])
        {
            swap(U[i],V[i]);
        }
        id_data[tid[U[i]]] = W[i];
    }
    build(1, 1, n);

    while(p--)
    {
        int a, b, c;
        scanf("%d",&c);
        if(c == 0)
        {
            scanf("%d",&a);
            printf("%d\n",Query(s,a));
            s = a;
        }
        else
        {
            scanf("%d %d", &a, &b);
            updata(1, 1, n, tid[U[a]], b);
        }
    }
}

int main()
{
    scanf("%d %d %d", &n, &p, &s);
    init();
    solve();

}