Aladdin and the Return Journey LightOJ - 1348

版权声明：本文为博主原创文章，未经博主允许不得转载。 https://blog.csdn.net/qq_36616023/article/details/82468682

题意：
一棵树，有n个点，每个点都有一个权值，有两种操作，

0 a b ，问从节点a到节点b路径上所有点权值和，

1 a b，把节点a权值改为b

点的树链剖分+点更新+区间查询

#include<bits/stdc++.h>
using namespace std;
const int maxn=35010;
struct edge
{
    int to,nxt;
}edge[maxn*2];
int head[maxn],tot;
int ee[maxn];
int top[maxn],fa[maxn],deep[maxn],num[maxn],p[maxn],fp[maxn],son[maxn],pos;
void init()
{
    tot=0;
    memset(head,-1,sizeof(head));
    pos=0;
    memset(son,-1,sizeof(son));
}
void add_edge(int u,int v)
{
    edge[tot].to=v;
    edge[tot].nxt=head[u];
    head[u]=tot++;
}
void dfs1(int u,int pre,int d) //???dfs??fa,deep,num,son
{
    deep[u] = d;
    fa[u] = pre;
    num[u] = 1;
    for(int i = head[u];i != -1;i = edge[i].nxt)
    {
        int v = edge[i].to;
        if(v != pre)
        {
            dfs1(v,u,d+1);
            num[u] += num[v];
            if(son[u] == -1 || num[v] > num[son[u]])
                son[u] = v;
        }
    }
}


void getpos(int u,int sp)
{
    top[u]=sp;
    p[u]=pos++;
    fp[p[u]]=u;
    if(son[u] == -1) return;
    getpos(son[u],sp);
    for(int i=head[u];i!=-1;i=edge[i].nxt)
    {
        int v=edge[i].to;
        if(v!=son[u]&&v!=fa[u])
            getpos(v,v);
    }
}
struct Node
{
    int l,r;
    int summ;
}segtree[maxn*3];
void push_up(int i)
{
    segtree[i].summ = segtree[i<<1].summ + segtree[(i<<1)|1].summ;
}
void build(int i,int l,int r)
{
    segtree[i].l = l;
    segtree[i].r = r;
    if(l == r)
    {
        segtree[i].summ = ee[fp[l]];
        return ;
    }
    int mid = (l + r)/2;
    build(i<<1,l,mid);
    build((i<<1)|1,mid+1,r);
    push_up(i);
}

void update(int i,int k,int val)//???????k???val
{
    if(segtree[i].l == k && segtree[i].r == k)
    {
        segtree[i].summ  = val;
        return;
    }
    int mid = (segtree[i].l + segtree[i].r)/2;
    if(k <= mid)update(i<<1,k,val);
    else update((i<<1)|1,k,val);
    push_up(i);
}
int query2(int i,int l,int r)
{
    if(segtree[i].l==l&&segtree[i].r==r)
        return segtree[i].summ;
    int mid=(segtree[i].l+segtree[i].r)/2;
    if(r<=mid)
        return query2(i<<1,l,r);
    else if(l>mid)
        return query2((i<<1)|1,l,r);
    else
        return query2(i<<1,l,mid)+query2((i<<1)|1,mid+1,r);
}
int findd2(int u,int v) //??u->v??????????
{
    int f1 = top[u], f2 = top[v];
    int tmp = 0;
    while(f1 != f2)
    {
        if(deep[f1] < deep[f2])
        {
            swap(f1,f2);
            swap(u,v);
        }
        tmp += query2(1,p[f1],p[u]);
        u = fa[f1];
        f1 = top[u];
    }
    if(deep[u] > deep[v]) swap(u,v);
    return tmp + query2(1,p[u],p[v]);
}
int main ()
{
    int T;
    int n;
    scanf("%d",&T);
    int icase=0;
    while(T--)
    {
        init();
        ++icase;
        scanf("%d",&n);
        for(int i=1;i<=n;i++)
        {
            scanf("%d",&ee[i]);
        }
        for(int i=0;i<n-1;i++)
        {
            int xx,yy;
            scanf("%d %d",&xx,&yy);
            xx++,yy++;
            add_edge(xx,yy);
            add_edge(yy,xx);
        }

        dfs1(1,0,0);
        getpos(1,1);
        build(1,0,pos-1);
        int op;
        int u,v;
        int opp;
        cin>>opp;
        printf("Case %d:\n",icase);
        while(opp--)
        {
            scanf("%d",&op);
            scanf("%d%d",&u,&v);
            if(op==0)
                u++,v++,printf("%d\n",findd2(u,v));
            else
                u++,update(1,p[u],v);
        }
    }
    return 0;
}