【SDOI2015第1轮第1试】寻宝游戏

#include<cstdio>
#include<set>
using namespace std;
typedef long long LL;

const int N = 1e5;
int top[N + 5] , dfn[N + 5] , rev[N + 5] , fa[N + 5] , size[N + 5] , son[N + 5] , dep[N + 5];
LL dis[N + 5] , ans , now;
int vis[N + 5] , h[N + 5] , n , m , tot = 1 , cnt;
struct node1{
    int to , nxt , w;
}e[(N << 1) + 5];
set<int> list;
set<int>::iterator it;

inline int read()
{
    char ch = getchar();
    int res = 0;
    for(; ch < '0' || ch > '9'; ch = getchar());
    for(; ch >= '0' && ch <= '9'; ch = getchar()) res = (res << 3) + (res << 1) + ch - '0';
    return res;
}

inline void add(int x , int y , int z)
{
    e[++tot].to = y;
    e[tot].w = z;
    e[tot].nxt = h[x];
    h[x] = tot;
}

inline void dfs1(int x , int f , int d)
{
    dep[x] = d;
    dfn[x] = ++cnt;
    rev[cnt] = x;
    fa[x] = f;
    size[x] = 1;
    for(register int i = h[x]; i; i = e[i].nxt)
    {
        int v = e[i].to;
        if (v == f) continue;
        dis[v] = dis[x] + 1LL * e[i].w;
        dfs1(v , x , d + 1);
        size[x] += size[v];
        if (size[v] > size[son[x]]) son[x] = v;
    }
}

inline void dfs2(int x , int f , int t)
{
    top[x] = t;
    if (son[x] > 0) dfs2(son[x] , x , t);
    for(register int i = h[x]; i; i = e[i].nxt)
    {
        int v = e[i].to;
        if (v == f || v == son[x]) continue;
        dfs2(v , x , v);
    }
}

inline int query(int x , int y)
{
    int fx = top[x] , fy = top[y];
    while (fx != fy)
    {
        if (dep[fx] >= dep[fy]) x = fa[fx] , fx = top[x];
        else y = fa[fy] , fy = top[y];
    }
    if (dep[x] <= dep[y]) return x;
    return y;
}

inline LL ask(int x , int y)
{
    return dis[x] + dis[y] - 2 * dis[query(x , y)];
}

int main()
{
//  freopen("寻宝游戏.in" , "r" , stdin);
    n = read() , m = read();
    int x , y , z;
    for(register int i = 1; i < n; i++)
    {
        x = read() , y = read() , z = read();
        add(x , y , z) , add(y , x , z);
    }
    dfs1(1 , 0 , 1) , dfs2(1 , 0 , 1);
    for(register int i = 1; i <= m; i++)
    {
        x = read();
        x = dfn[x];
        if (!vis[rev[x]]) list.insert(x);
        y = rev[(it = list.lower_bound(x)) == list.begin() ? *--list.end() : *--it];
        z = rev[(it = list.upper_bound(x)) == list.end() ? *list.begin() : *it];
        if (vis[rev[x]]) list.erase(x);
        x = rev[x];
        now = ask(y , x) + ask(x , z) - ask(y , z);
        if (!vis[x]) vis[x] = 1 , ans += now;
        else vis[x] = 0 , ans -= now;
        printf("%lld\n" , ans);
    }
}

原文地址：https://www.cnblogs.com/leiyuanze/p/12337082.html