🔺Count on a tree SPOJ

https://cn.vjudge.net/problem/SPOJ-COT

插上 大佬的代码 和 我的。。。以后再看吧。。。

Count on a tree

大佬：http://www.cnblogs.com/Sunnie69/p/5511684.html

#include <cstdio>
#include <algorithm>
#include <vector>
using namespace std;

const int maxn=100000+5;
int n,m,cnt,num;
int a[maxn],id[maxn],b[maxn],head[maxn],p[maxn],f[maxn],root[maxn];
bool vis[maxn];
struct edge{
    int to,next;
    edge(){}
    edge(int a,int b):to(a),next(b){}
}g[maxn<<1];
struct Qry{
    int u,v,k,lca;
    Qry(){}
    Qry(int a,int b,int c,int d):u(a),v(b),k(c),lca(d){}
}Q[maxn];
struct node{ int l,r,s; }t[maxn*20];
struct qry{
    int v,id;
    qry(){}
    qry(int a,int b):v(a),id(b){}
};
vector <qry> q[maxn];

inline int find(int x){ return x==f[x]?x:f[x]=find(f[x]); }
void add_edge(int u,int v){
    g[++cnt]=edge(v,head[u]); head[u]=cnt;
    g[++cnt]=edge(u,head[v]); head[v]=cnt;
}
void update(int l,int r,int &pos,int d){
    t[++num]=t[pos]; pos=num; t[pos].s++; 
    if(l==r) return;
    int mid=l+(r-l)/2;
    if(d<=mid) update(l,mid,t[pos].l,d);
    else update(mid+1,r,t[pos].r,d);
}
bool cmp(int x,int y){ return a[x]<a[y]; }
void dfs(int u){
    f[u]=u; root[u]=root[p[u]]; update(1,n,root[u],b[u]);
    for(int i=head[u];i;i=g[i].next){
        if(g[i].to!=p[u]){
            p[g[i].to]=u;
            dfs(g[i].to);
            f[g[i].to]=u;
        }
    }
    vis[u]=true;
    int size=q[u].size();
    for(int i=0;i<size;i++) if(vis[q[u][i].v]) Q[q[u][i].id].lca=find(q[u][i].v);
}
void init(){
    scanf("%d%d",&n,&m);
    for(int i=1;i<=n;i++) scanf("%d",&a[i]), id[i]=i;
    sort(id+1,id+n+1,cmp);
    for(int i=1;i<=n;i++) b[id[i]]=i;
    for(int i=1;i<n;i++){
        int u,v;
        scanf("%d%d",&u,&v);
        add_edge(u,v);
    }
    for(int i=1;i<=m;i++){
        scanf("%d%d%d",&Q[i].u,&Q[i].v,&Q[i].k);
        q[Q[i].u].push_back(qry(Q[i].v,i)); q[Q[i].v].push_back(qry(Q[i].u,i));
    }
}
int query(int l,int r,int x,int y,int ra,int a,int k){
    if(l==r) return l;
    int mid=l+(r-l)/2;
    int s=t[t[x].l].s+t[t[y].l].s-2*t[t[ra].l].s;
    if(b[a]>=l&&b[a]<=mid) s++;
    if(k<=s) return query(l,mid,t[x].l,t[y].l,t[ra].l,a,k);
    else return query(mid+1,r,t[x].r,t[y].r,t[ra].r,a,k-s);
}
void solve(){
    dfs(1);
    for(int i=1;i<=m;i++){
        if(Q[i].u==Q[i].v){ printf("%d
",a[Q[i].u]); continue; }
        printf("%d
",a[id[query(1,n,root[Q[i].u],root[Q[i].v],root[Q[i].lca],Q[i].lca,Q[i].k)]]);
    }
}
int main(){
    init();
    solve();
    return 0;
}

蒟蒻：

#include <iostream>
#include <cstdio>
#include <sstream>
#include <cstring>
#include <map>
#include <set>
#include <vector>
#include <stack>
#include <queue>
#include <algorithm>
#include <cmath>
#define rap(a, n) for(int i=a; i<=n; i++)
#define MOD 2018
#define LL long long
#define ULL unsigned long long
#define Pair pair<int, int>
#define mem(a, b) memset(a, b, sizeof(a))
#define _  ios_base::sync_with_stdio(0),cin.tie(0)
//freopen("1.txt", "r", stdin);
using namespace std;
const int maxn = 10010, INF = 0x7fffffff;
int n, m, x, y, k, cnt;
int root[maxn], a[maxn], f[maxn], head[maxn], vis[maxn], pre[maxn];
struct node {int l, r, sum;}T[maxn];
struct edge {int v, next, lca;}Edge[maxn];
vector<int> v;
int getid(int x) { return lower_bound(v.begin(), v.end(), x) - v.begin() + 1;}
vector<int> G[maxn];

struct quer {int u, v, id, lca, k;}Q[maxn];
vector<quer> q[maxn];
void add_(int u, int v)
{
    Edge[cnt].v = v;
    Edge[cnt].next = head[u];
    head[u] = cnt++;
}
void add(int u, int v)
{
    add_(u, v);
    add_(v, u);
}

int find(int x)
{
    return f[x] == x?x:(f[x] == find(f[x]));
}

void update(int l, int r, int& pos, int d)
{
    T[++cnt] = T[pos], T[cnt].sum++, pos = cnt;
    if(l == r) return;
    int mid = l + (r - l) / 2;
    if(mid >= d) update(l, mid, T[pos].l, d);
    else update(mid+1, r, T[pos].r, d);
}

void lca(int u)
{
    f[u] = u;
    root[u] = root[pre[u]];
    update(1, n, root[u], getid(u));
    for(int i=head[u]; i!=-1; i=Edge[i].next)
    {
        int v = Edge[i].v;
        if(v == pre[u]) continue;
        pre[v] = u;
        lca(v);
        f[v] = u;
    }
    vis[u] = true;
    int size = q[u].size();
    rap(0, size-1)
    {
        if(vis[q[u][i].v])
        {
            Q[q[u][i].id].lca = find(q[u][i].v);
        }
    }
}

int query(int l, int r, int x, int y, int ra, int lca, int k)
{
    if(l == r) return l;
    int mid = l + (r - l) / 2;
    int sum = T[T[y].l].sum + T[T[x].l].sum - 2*T[T[ra].l].sum;
    int lca_id = getid(lca);
    if(lca_id >= l && lca_id <= mid) sum++;
    if(sum >= k) return query(l, mid, T[x].l, T[y].l, T[ra].l, lca, k);
    else return query(mid+1, r, T[x].r, T[y].r, T[ra].r, lca, k - sum);
}

int main()
{
    mem(head, -1);
    cnt = 0;
    scanf("%d%d", &n, &m);
    rap(1, n)
    {
        scanf("%d", &a[i]);
        v.push_back(a[i]);
    }
    sort(v.begin(), v.end()); v.erase(unique(v.begin(), v.end()), v.end());
    rap(1, n-1)
    {
        int u, v;
        scanf("%d%d", &u, &v);
        add(u, v);
    }
    rap(1, m)
    {
        scanf("%d%d%d", &Q[i].u, &Q[i].v, &Q[i].k);
        Q[i].id = i;
        q[Q[i].u].push_back(Q[i]);
        q[Q[i].v].push_back(Q[i]);
    }
    lca(1);
    rap(1, m)
    {
        if(Q[i].u == Q[i].v)
        {
            printf("%d
",a[Q[i].u]);
            continue;
        }

        printf("%d
",v[query(1, n, root[Q[i].u], root[Q[i].v], root[Q[i].lca], Q[i].lca, Q[i].k) - 1]);
    }
    return 0;
}