Tree POJ - 3237

​​http://poj.org/problem?id=3237​​​​​​​

#include <cstdio>
#include <cstring>
#include <algorithm>
using namespace std;
#define N 0x3f3f3f3f

struct node1
{
    int u;
    int v;
    int w;
};

struct node2
{
    int v;
    int next;
};

struct node3
{
    int l;
    int r;
    int laz;
    int maxx;
    int minn;
};

node1 pre[10010];
node2 edge[20010];
node3 tree[40010];
int val[10010],first[10010],fa[10010],deep[10010],sum[10010],son[10010],top[10010],mp1[10010],mp2[10010];
int n,num;

void addedge(int u,int v)
{
    edge[num].v=v;
    edge[num].next=first[u];
    first[u]=num++;
}

void dfsI(int cur)
{
    int i,v;
    sum[cur]=1,son[cur]=-1;
    for(i=first[cur];i!=-1;i=edge[i].next)
    {
        v=edge[i].v;
        if(v!=fa[cur])
        {
            fa[v]=cur,deep[v]=deep[cur]+1;
            dfsI(v);
            sum[cur]+=sum[v];
            if(son[cur]==-1||sum[son[cur]]<sum[v])
            {
                son[cur]=v;
            }
        }
    }
}

void dfsII(int cur,int tp)
{
    int i,v;
    num++;
    top[cur]=tp,mp1[cur]=num,mp2[num]=cur;
    if(son[cur]==-1) return;
    dfsII(son[cur],tp);
    for(i=first[cur];i!=-1;i=edge[i].next)
    {
        v=edge[i].v;
        if(v!=fa[cur]&&v!=son[cur])
        {
            dfsII(v,v);
        }
    }
}

void pushup(int cur)
{
    tree[cur].maxx=max(tree[2*cur].maxx,tree[2*cur+1].maxx);
    tree[cur].minn=min(tree[2*cur].minn,tree[2*cur+1].minn);
}

void pushdown(int cur)
{
    if(tree[cur].laz==-1)
    {
        tree[2*cur].maxx*=-1,tree[2*cur].minn*=-1;
        swap(tree[2*cur].maxx,tree[2*cur].minn);
        tree[2*cur].laz*=-1;
        tree[2*cur+1].maxx*=-1,tree[2*cur+1].minn*=-1;
        swap(tree[2*cur+1].maxx,tree[2*cur+1].minn);
        tree[2*cur+1].laz*=-1;
        tree[cur].laz=1;
    }
}

void build(int l,int r,int cur)
{
    int m;
    tree[cur].l=l;
    tree[cur].r=r;
    tree[cur].laz=1;
    tree[cur].maxx=-N;
    tree[cur].minn=N;
    if(l==r)
    {
        tree[cur].maxx=val[mp2[l]];
        tree[cur].minn=val[mp2[l]];
        return;
    }
    m=(l+r)/2;
    build(l,m,2*cur);
    build(m+1,r,2*cur+1);
    pushup(cur);
}

void updateI(int tar,int val,int cur)
{
    if(tree[cur].l==tree[cur].r)
    {
        tree[cur].maxx=val;
        tree[cur].minn=val;
        return;
    }
    pushdown(cur);
    if(tar<=tree[2*cur].r) updateI(tar,val,2*cur);
    else updateI(tar,val,2*cur+1);
    pushup(cur);
}

void updateII(int pl,int pr,int cur)
{
    if(pl<=tree[cur].l&&tree[cur].r<=pr)
    {
        tree[cur].maxx*=-1,tree[cur].minn*=-1;
        swap(tree[cur].maxx,tree[cur].minn);
        tree[cur].laz*=-1;
        return;
    }
    pushdown(cur);
    if(pl<=tree[2*cur].r) updateII(pl,pr,2*cur);
    if(pr>=tree[2*cur+1].l) updateII(pl,pr,2*cur+1);
    pushup(cur);
}

void solveI(int u,int v)
{
    while(top[u]!=top[v])
    {
        if(deep[top[u]]<deep[top[v]]) swap(u,v);
        updateII(mp1[top[u]],mp1[u],1);
        u=fa[top[u]];
    }
    if(u==v) return;
    if(deep[u]<deep[v]) swap(u,v);
    updateII(mp1[son[v]],mp1[u],1);
}

int query(int pl,int pr,int cur)
{
    int res;
    if(pl<=tree[cur].l&&tree[cur].r<=pr)
    {
        return tree[cur].maxx;
    }
    pushdown(cur);
    res=-N;
    if(pl<=tree[2*cur].r) res=max(res,query(pl,pr,2*cur));
    if(pr>=tree[2*cur+1].l) res=max(res,query(pl,pr,2*cur+1));
    return res;
}

int solveII(int u,int v)
{
    int res;
    res=-N;
    while(top[u]!=top[v])
    {
        if(deep[top[u]]<deep[top[v]]) swap(u,v);
        res=max(res,query(mp1[top[u]],mp1[u],1));
        u=fa[top[u]];
    }
    if(u==v) return res;
    if(deep[u]<deep[v]) swap(u,v);
    res=max(res,query(mp1[son[v]],mp1[u],1));
    return res;
}

int main()
{
    int t,i,u,v,w;
    char op[10];
    scanf("%d",&t);
    while(t--)
    {
        scanf("%d",&n);
        memset(first,-1,sizeof(first));
        num=0;
        for(i=1;i<=n-1;i++)
        {
            scanf("%d%d%d",&pre[i].u,&pre[i].v,&pre[i].w);
            addedge(pre[i].u,pre[i].v);
            addedge(pre[i].v,pre[i].u);
        }
        fa[1]=-1,deep[1]=1;
        dfsI(1);
        num=0;
        dfsII(1,1);
        val[1]=-N;
        for(i=1;i<=n-1;i++)
        {
            if(deep[pre[i].u]<deep[pre[i].v]) swap(pre[i].u,pre[i].v);
            val[pre[i].u]=pre[i].w;
        }
        build(1,n,1);
        while(1)
        {
            scanf("%s",op);
            if(op[0]=='C')
            {
                scanf("%d%d",&i,&w);
                updateI(mp1[pre[i].u],w,1);
            }
            else if(op[0]=='N')
            {
                scanf("%d%d",&u,&v);
                solveI(u,v);
            }
            else if(op[0]=='Q')
            {
                scanf("%d%d",&u,&v);
                printf("%d\n",solveII(u,v));
            }
            else break;
        }
    }
    return 0;
}