AC日记——Tree poj 3237

Tree
Time Limit: 5000MS   Memory Limit: 131072K
Total Submissions: 9233   Accepted: 2431

Description

You are given a tree with N nodes. The tree’s nodes are numbered 1 through N and its edges are numbered 1 through N − 1. Each edge is associated with a weight. Then you are to execute a series of instructions on the tree. The instructions can be one of the following forms:

CHANGE i v Change the weight of the ith edge to v
NEGATE a b Negate the weight of every edge on the path from a to b
QUERY a b Find the maximum weight of edges on the path from a to b

Input

The input contains multiple test cases. The first line of input contains an integer t (t ≤ 20), the number of test cases. Then follow the test cases.

Each test case is preceded by an empty line. The first nonempty line of its contains N (N ≤ 100,000). The next N − 1 lines each contains three integers ab and c, describing an edge connecting nodes a and b with weight c. The edges are numbered in the order they appear in the input. Below them are the instructions, each sticking to the specification above. A lines with the word “DONE” ends the test case.

Output

For each “QUERY” instruction, output the result on a separate line.

Sample Input

1

3
1 2 1
2 3 2
QUERY 1 2
CHANGE 1 3
QUERY 1 2
DONE

Sample Output

1
3

Source

 
思路:
  树剖边权转点权;
  边权赋值到边上深度较大的点;
  然后有个取反操作,就是相反数;
  我们记录max和min;
  每次取反交换max和min;
  然后乘以-1;
  轻松ac(不知道wa了多少次);
 
来,上代码:
#include <cstdio>
#include <cstring>
#include <iostream>
#include <algorithm>

#define maxn 1000005

using namespace std;

struct TreeNodeType {
    int l,r,dis,dis_,mid,flag;
};
struct TreeNodeType tree[maxn<<2];

struct EdgeType {
    int v,w,next;
};
struct EdgeType edge[maxn<<1];

int u_[maxn],v_[maxn];
int if_z,t,n,cnt,head[maxn],deep[maxn],f[maxn];
int flag[maxn],top[maxn],size[maxn],dis[maxn],dis_[maxn];

char Cget;

inline void in(int &now)
{
    now=0,if_z=1,Cget=getchar();
    while(Cget>'9'||Cget<'0')
    {
        if(Cget=='-') if_z=-1;
        Cget=getchar();
    }
    while(Cget>='0'&&Cget<='9')
    {
        now=now*10+Cget-'0';
        Cget=getchar();
    }
    now*=if_z;
}

inline void edge_add(int u,int v,int w)
{
    edge[++cnt].v=v,edge[cnt].w=w,edge[cnt].next=head[u],head[u]=cnt;
    edge[++cnt].v=u,edge[cnt].w=w,edge[cnt].next=head[v],head[v]=cnt;
}

void search_1(int now,int fa)
{
    int pos=cnt++;
    deep[now]=deep[fa]+1,f[now]=fa;
    for(int i=head[now];i;i=edge[i].next)
    {
        if(edge[i].v==fa) continue;
        dis_[edge[i].v]=edge[i].w;
        search_1(edge[i].v,now);
    }
    size[now]=cnt-pos;
}

void search_2(int now,int chain)
{
    int pos=0;
    top[now]=chain;
    flag[now]=++cnt;
    dis[flag[now]]=dis_[now];
    for(int i=head[now];i;i=edge[i].next)
    {
        if(edge[i].v==f[now]) continue;
        if(size[edge[i].v]>size[pos]) pos=edge[i].v;
    }
    if(pos==0) return ;
    search_2(pos,chain);
    for(int i=head[now];i;i=edge[i].next)
    {
        if(edge[i].v==f[now]||edge[i].v==pos) continue;
        search_2(edge[i].v,edge[i].v);
    }
}

inline void tree_up(int now)
{
    tree[now].dis=max(tree[now<<1].dis,tree[now<<1|1].dis);
    tree[now].dis_=min(tree[now<<1].dis_,tree[now<<1|1].dis_);
}

inline void tree_down(int now)
{
    if(tree[now].l==tree[now].r) return ;
    tree[now<<1].dis*=-1,tree[now<<1|1].dis*=-1;
    tree[now<<1].dis_*=-1,tree[now<<1|1].dis_*=-1;
    tree[now<<1].flag*=-1,tree[now<<1|1].flag*=-1;
    swap(tree[now<<1].dis_,tree[now<<1].dis);
    swap(tree[now<<1|1].dis_,tree[now<<1|1].dis);
    tree[now].flag=1;return ;
}

void tree_build(int now,int l,int r)
{
    tree[now].l=l,tree[now].r=r,tree[now].flag=1;
    if(l==r)
    {
        tree[now].dis=dis[l];
        tree[now].dis_=tree[now].dis;
        return ;
    }
    tree[now].mid=(l+r)>>1;
    tree_build(now<<1,l,tree[now].mid);
    tree_build(now<<1|1,tree[now].mid+1,r);
    tree_up(now);
}

void tree_change(int now,int to,int x)
{
    if(tree[now].l==tree[now].r)
    {
        tree[now].dis=x;
        tree[now].dis_=x;
        return ;
    }
    if(tree[now].flag==-1) tree_down(now);
    if(to<=tree[now].mid) tree_change(now<<1,to,x);
    else tree_change(now<<1|1,to,x);
    tree_up(now);
}

void tree_negate(int now,int l,int r)
{
    if(tree[now].l==l&&tree[now].r==r)
    {
        tree[now].dis*=-1;
        tree[now].dis_*=-1;
        swap(tree[now].dis,tree[now].dis_);
        tree[now].flag*=-1;
        return ;
    }
    if(tree[now].flag==-1) tree_down(now);
    if(l>tree[now].mid) tree_negate(now<<1|1,l,r);
    else if(r<=tree[now].mid) tree_negate(now<<1,l,r);
    else
    {
        tree_negate(now<<1,l,tree[now].mid);
        tree_negate(now<<1|1,tree[now].mid+1,r);
    }
    tree_up(now);
}

int tree_query(int now,int l,int r)
{
    if(tree[now].l==l&&tree[now].r==r)
    {
        return tree[now].dis;
    }
    if(tree[now].flag==-1) tree_down(now);
    if(l>tree[now].mid) return tree_query(now<<1|1,l,r);
    else if(r<=tree[now].mid) return tree_query(now<<1,l,r);
    else
    {
        return max(tree_query(now<<1,l,tree[now].mid),tree_query(now<<1|1,tree[now].mid+1,r));
    }
}

int solve_query(int x,int y)
{
    int pos=-0x7ffffff;
    while(top[x]!=top[y])
    {
        if(deep[top[x]]<deep[top[y]]) swap(x,y);
        pos=max(pos,tree_query(1,flag[top[x]],flag[x]));
        x=f[top[x]];
    }
    if(x==y) return pos;
    if(deep[x]>deep[y]) swap(x,y);
    pos=max(pos,tree_query(1,flag[x]+1,flag[y]));
    return pos;
}

void solve_negate(int x,int y)
{
    while(top[x]!=top[y])
    {
        if(deep[top[x]]<deep[top[y]]) swap(x,y);
        tree_negate(1,flag[top[x]],flag[x]);
        x=f[top[x]];
    }
    if(x==y) return ;
    if(deep[x]>deep[y]) swap(x,y);
    tree_negate(1,flag[x]+1,flag[y]);
}

int main()
{
    in(t);
    while(t--)
    {
        memset(head,0,sizeof(head));
        in(n);cnt=0;
        int u,v,w;char ch[10];
        for(int i=1;i<n;i++)
        {
            in(u),in(v),in(w);
            u_[i]=u,v_[i]=v,edge_add(u,v,w);
        }
        cnt=0,search_1(1,0);
        cnt=0,search_2(1,1);
        tree_build(1,1,n);
        for(int i=1;i<n;i++)
        {
            if(deep[u_[i]]<deep[v_[i]]) swap(u_[i],v_[i]);
        }
        while(1)
        {
            cin>>ch;
            if(ch[0]=='D') break;
            in(u),in(v);
            if(ch[0]=='N') solve_negate(u,v);
            if(ch[0]=='C') tree_change(1,flag[u_[u]],v);
            if(ch[0]=='Q')
            {
                cout<<solve_query(u,v);
                putchar('\n');
            }
        }
    }
    return 0;
}

 

posted @ 2017-02-19 08:47  IIIIIIIIIU  阅读(190)  评论(0编辑  收藏  举报