poj 3237 Tree(树链剖分)

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#include <iostream>
#include <cstdio>
#include <cstring>
#include <algorithm>
#include <queue>
using namespace std;
typedef long long ll;
#define lson l,m,rt<<1
#define rson m+1,r,rt<<1|1
const int N = 10010;
const int INF = 1<<30;
int _, n, pre[N], fa[N], sz[N], top[N];
int gid, dep[N], son[N], id[N], fid[N];
int Max[N<<2], Min[N<<2], neg[N<<2];

struct edge
{
    int u, v, w, next;
    edge() {}
    edge(int u, int v,int w, int next):u(u),v(v),w(w),next(next) {}
}e[N<<1];
int ecnt;

inline void addedge(int u, int v, int w)
{
    e[ecnt] = edge(u, v, w, pre[u]);
    pre[u] = ecnt++;
    e[ecnt] = edge(v, u, w, pre[v]);
    pre[v] = ecnt++;
}

inline void dfs(int u, int f, int d)
{
    sz[u]=1, fa[u]=f, dep[u]=d, son[u]=0;
    for(int i=pre[u]; ~i; i=e[i].next)
    {
        int v = e[i].v;
        if(v==f) continue;
        dfs(v, u, d+1);
        sz[u] += sz[v];
        if(sz[son[u]]<sz[v]) son[u] = v;
    }
}

inline void fxor(int &x)
{
    x = x==INF?-INF:INF;
}

inline void getpos(int u, int f)
{
    id[u] = ++gid;
    fid[gid] = u;
    top[u] = f;
    if(son[u]==0) return ;
    getpos(son[u], f);
    for(int i=pre[u]; ~i; i=e[i].next)
    {
        int v = e[i].v;
        if(v==fa[u] || v==son[u]) continue;
        getpos(v, v);
    }
}

inline void Up(int rt)
{
    Max[rt] = max(Max[rt<<1], Max[rt<<1|1]);
    Min[rt] = min(Min[rt<<1], Min[rt<<1|1]);
}

inline void build(int l, int r, int rt)
{
    neg[rt] = Min[rt] = INF, Max[rt] = -INF;
    if(l==r) return ;
    int m = (l+r)>>1;
    build(lson);
    build(rson);
}

inline void Down(int rt)
{
    if(neg[rt]==-INF)
    {
        int ls=rt<<1, rs=ls|1;
        fxor(neg[ls]), fxor(neg[rs]);
        Min[ls] = -Min[ls];
        Max[ls] = -Max[ls];
        swap(Max[ls], Min[ls]);
        Min[rs] = -Min[rs];
        Max[rs] = -Max[rs];
        swap(Max[rs], Min[rs]);
        neg[rt] = INF;
    }
}

inline void update(int L, int R, int c, int l, int r, int rt)
{
    if(L<=l && R>=r){
        if(c>-INF) Min[rt] = Max[rt] = c;
        else{
            fxor(neg[rt]);
            Min[rt] = -Min[rt];
            Max[rt] = -Max[rt];
            swap(Min[rt], Max[rt]);
        }
        return ;
    }
    Down(rt);
    int m = (l+r)>>1;
    if(L<=m) update(L, R, c, lson);
    if(R>m) update(L, R, c, rson);
    Up(rt);
}

inline int query(int L, int R, int l, int r, int rt)
{
    if(L<=l && r<=R) return Max[rt];
    Down(rt);
    int m = (l+r)>>1;
    int ans = -INF;
    if(L<=m) ans = max(ans, query(L, R, lson));
    if(R>m) ans = max(ans, query(L, R, rson));
    return ans;
}

inline int lcaQ(int u, int v, bool flag)
{
    int fu=top[u], fv=top[v];
    int ans = -INF;
    while(fv!=fu)
    {
        if(dep[fu]<dep[fv])
        {
            swap(fv, fu); swap(u, v);
        }
        if(flag) ans = max(ans,query(id[fu], id[u], 1, gid, 1));
        else update(id[fu], id[u], -INF, 1, gid, 1);
        u = fa[fu];
        fu = top[u];
    }
    if(dep[u]<dep[v]) swap(u,v);
    if(u!=v)
    {
        if(flag) ans = max(ans, query(id[v]+1, id[u], 1, gid, 1));
        else update(id[v]+1, id[u], -INF, 1, gid, 1);
    }
    return ans;
}

inline void solve()
{
    ecnt = 0, gid = 0;
    memset(pre, -1, sizeof(pre));
    scanf("%d", &n);
    int u, v, w;
    for(int i=1; i<n; i++)
    {
        scanf("%d%d%d", &u, &v, &w);
        addedge(u, v, w);
    }
    sz[0] = 0;
    dfs(1, 1, 0);
    getpos(1, 1);

    build(1, gid , 1);
    for(int i=1; i<ecnt; i+=2)
    {
        if(dep[e[i].u] < dep[e[i].v]) swap(e[i].u, e[i].v);
        update(id[e[i].u], id[e[i].u], e[i].w, 1, gid, 1);
    }

    char str[15];
    while(scanf("%s", str)>0 && str[0]!=‘D‘)
    {
        scanf("%d%d", &u, &v);
        if(str[0]==‘Q‘)
            printf("%d\n",lcaQ(u, v, 1));
        else if(str[0]==‘N‘)
            lcaQ(u, v, 0);
        else
            update(id[e[2*u-1].u], id[e[2*u-1].u], v, 1, gid, 1);
    }
}

int main()
{
//    freopen("in.txt", "r", stdin);
    cin>>_;
    while(_--) solve();
    return 0;
}