[国家集训队]旅游

嘟嘟嘟

这其实就是一道树剖板子题，只不过就是写的长了一点。

还是叨叨几点吧：

1.区间取相反数：开一个标记数组，每一次亦或1，然后对应的sum取相反数，Max, Min交换，并且取相反数。

2.题目中给的是边权，但要转化成点权：这条边的边权转化成儿子节点的点权，然后每一次链上操作的时候，x, y的LCA不要管。实现的时候就是当x,y跳到同一条链的时候，对[dfsx[y] + 1, dfsx[x]]（假设dfsx[y] < dfsx[x]）操作即可，因为同一条链上的dfs序是连续的。

耐着性子写完吧~

#include<cstdio>
#include<iostream>
#include<cmath>
#include<algorithm>
#include<cstring>
#include<cstdlib>
#include<cctype>
#include<vector>
#include<stack>
#include<queue>
using namespace std;
#define enter puts("") 
#define space putchar(' ')
#define Mem(a, x) memset(a, x, sizeof(a))
#define rg register
typedef long long ll;
typedef double db;
const int INF = 0x3f3f3f3f;
const db eps = 1e-8;
const int maxn = 1e5 + 5;
inline ll read()
{
    ll ans = 0;
    char ch = getchar(), last = ' ';
    while(!isdigit(ch)) {last = ch; ch = getchar();}
    while(isdigit(ch)) {ans = ans * 10 + ch - '0'; ch = getchar();}
    if(last == '-') ans = -ans;
    return ans;
}
inline void write(ll x)
{
    if(x < 0) x = -x, putchar('-');
    if(x >= 10) write(x / 10);
    putchar(x % 10 + '0');
}

int n, m, a[maxn];

vector<int> v[maxn], c[maxn];
bool vis[maxn];
int dep[maxn], fa[maxn], siz[maxn], son[maxn];
void dfs1(int now)
{
    vis[now] = 1; siz[now] = 1;
    for(int i = 0; i < (int)v[now].size(); ++i)
    {
        if(!vis[v[now][i]])
        {
            a[v[now][i]] = c[now][i];
            dep[v[now][i]] = dep[now] + 1;
            fa[v[now][i]] = now;
            dfs1(v[now][i]);
            siz[now] += siz[v[now][i]];
            if(!son[now] || siz[son[now]] < siz[v[now][i]]) son[now] = v[now][i];
        }
    }
}
int dfsx[maxn], pos[maxn], top[maxn], cnt = 0;
void dfs2(int now)
{
    vis[now] = 1;
    dfsx[now] = ++cnt; pos[cnt] = now;
    if(son[now])
    {
        top[son[now]] = top[now];
        dfs2(son[now]);
    }
    for(int i = 0; i < (int)v[now].size(); ++i)
    {
        if(!vis[v[now][i]] && v[now][i] != son[now])
        {
            top[v[now][i]] = v[now][i];
            dfs2(v[now][i]);
        }
    }
}

int l[maxn << 2], r[maxn << 2], sum[maxn << 2], Max[maxn << 2], Min[maxn << 2];
int lzy[maxn << 2];             //相反数标记
void pushup(int now)
{
    sum[now] = sum[now << 1] + sum[now << 1 | 1];
    Max[now] = max(Max[now << 1], Max[now << 1 | 1]);
    Min[now] = min(Min[now << 1], Min[now << 1 | 1]);    
}
void build(int L, int R, int now)
{
    l[now] = L; r[now] = R;
    if(L == R) {sum[now] = Max[now] = Min[now] = a[pos[L]]; return;}
    int mid = (L + R) >> 1;
    build(L, mid, now << 1);
    build(mid + 1, R, now << 1 | 1);
    pushup(now);
}
void pushdown(int now)
{
    if(lzy[now])
    {
        sum[now << 1] = -sum[now << 1]; sum[now << 1 | 1] = -sum[now << 1 | 1];
        swap(Max[now << 1], Min[now << 1]); swap(Max[now << 1 | 1], Min[now << 1 | 1]);
        Max[now << 1] = -Max[now << 1]; Max[now << 1 | 1] = -Max[now << 1 | 1];
        Min[now << 1] = -Min[now << 1]; Min[now << 1 | 1] = -Min[now << 1 | 1];
        lzy[now << 1] ^= 1; lzy[now << 1 | 1] ^= 1;
        lzy[now] = 0;
    }
    
}
void update_sin(int now, int idx, int d)
{
    if(l[now] == r[now]) 
    {
        sum[now] = Max[now] = Min[now] = d; 
        return;
    }
    pushdown(now);
    int mid = (l[now] + r[now]) >> 1;
    if(idx <= mid) update_sin(now << 1, idx, d);
    else update_sin(now << 1 | 1, idx, d);
    pushup(now);
}
void update_opp(int L, int R, int now)
{
    if(L == l[now] && R == r[now])
    {
        sum[now] = -sum[now];
        swap(Max[now], Min[now]);
        Max[now] = -Max[now];
        Min[now] = -Min[now];
        lzy[now] ^= 1;
        return;
    }
    pushdown(now);
    int mid = (l[now] + r[now]) >> 1;
    if(R <= mid) update_opp(L, R, now << 1);
    else if(L > mid) update_opp(L, R, now << 1 | 1);
    else update_opp(L, mid, now << 1), update_opp(mid + 1, R, now << 1 | 1);
    pushup(now);
}
int query_sum(int L, int R, int now)
{
    if(L == l[now] && R == r[now]) return sum[now];
    pushdown(now);
    int mid = (l[now] + r[now]) >> 1;
    if(R <= mid) return query_sum(L, R, now << 1);
    else if(L > mid) return query_sum(L, R, now << 1 | 1);
    else return query_sum(L, mid, now << 1) + query_sum(mid + 1, R, now << 1 | 1);
}
int query_M(int L, int R, int now, bool flg)
{
    if(L == l[now] && R == r[now]) return flg ? Max[now] : Min[now];
    pushdown(now);
    int mid = (l[now] + r[now]) >> 1;
    if(R <= mid) return query_M(L, R, now << 1, flg);
    else if(L > mid) return query_M(L, R, now << 1 | 1, flg);
    else
    {
        if(flg) return max(query_M(L, mid, now << 1, flg), query_M(mid + 1, R, now << 1 | 1, flg));
        else return min(query_M(L, mid, now << 1, flg), query_M(mid + 1, R, now << 1 | 1, flg));
    }
}

void update_path(int x, int y)
{
    while(top[x] != top[y])
    {
        if(dep[top[x]] < dep[top[y]]) swap(x, y);
        update_opp(dfsx[top[x]], dfsx[x], 1);
        x = fa[top[x]];
    }
    if(dfsx[x] < dfsx[y]) swap(x, y);
    if(x == y) return;
    update_opp(dfsx[y] + 1, dfsx[x], 1);
}
int queryS_path(int x, int y)
{
    int ret = 0;
    while(top[x] != top[y])
    {
        if(dep[top[x]] < dep[top[y]]) swap(x, y);
        ret += query_sum(dfsx[top[x]], dfsx[x], 1);
        x = fa[top[x]];
    }
    if(dfsx[x] < dfsx[y]) swap(x, y);
    if(x != y) ret += query_sum(dfsx[y] + 1, dfsx[x], 1);    
    return ret;
}
int queryM_path(int x, int y, int flg)
{
    int ret = flg ? -INF : INF;
    while(top[x] != top[y])
    {
        if(dep[top[x]] < dep[top[y]]) swap(x, y);
        if(flg) ret = max(ret, query_M(dfsx[top[x]], dfsx[x], 1, flg));
        else ret = min(ret, query_M(dfsx[top[x]], dfsx[x], 1, flg));
        x = fa[top[x]];
    }
    if(dfsx[x] < dfsx[y]) swap(x, y);
    if(x != y)
    {
        if(flg) ret = max(ret, query_M(dfsx[y] + 1, dfsx[x], 1, flg));
        else ret = min(ret, query_M(dfsx[y] + 1, dfsx[x], 1, flg));
    }
    return ret;
}

char ch[5];

int main()
{
    n = read();
    for(int i = 1; i < n; ++i)
    {
        int x = read() + 1, y = read() + 1, co = read();
        v[x].push_back(y); c[x].push_back(co);
        v[y].push_back(x); c[y].push_back(co);
    }
    dfs1(1); 
    Mem(vis, 0); top[1] = 1; dfs2(1);
    build(1, cnt, 1);
    m = read();
    for(int i = 1; i <= m; ++i)
    {
        scanf("%s", ch); int x = read() + 1, y = read() + 1;
        if(ch[0] == 'C') update_sin(1, dfsx[x], y - 1);
        else if(ch[0] == 'N') update_path(x, y);
        else if(ch[0] == 'S') write(queryS_path(x, y)), enter;
        else if(ch[1] == 'A') write(queryM_path(x, y, 1)), enter;
        else write(queryM_path(x, y, 0)), enter;
    }
    return 0;
}