【bzoj2733】 [HNOI2012] 永无乡

sb题
合并：并查集+线段树启发式合并，注意动态开点
查询：直接查对应线段树的K大。
时间复杂度 O(qlog2n)

#include <bits/stdc++.h>
using namespace std;
#define rep(i,a,b) for(int i=a,_=b;i<=_;i++)
#define per(i,a,b) for(int i=a,_=b;i>=_;i--)
#define maxn 200007
#define maxs 3000007

inline int rd() {
    char c = getchar();
    while (!isdigit(c)) c = getchar() ; int x = c - '0';
    while (isdigit(c = getchar())) x = x * 10 + c - '0';
    return x;
}

typedef int arr[maxn];
typedef int seg[maxs];

arr a , h , rt , fa , rk;
seg lc , rc , cnt , pool;
int s_tot , tot , n , m;

inline int newnode() {
    /*if (s_tot) return pool[s_tot --]; else return ++ tot;*/
    return ++ tot;
}

inline void delnode(int t) {
    cnt[t] = 0 , lc[t] = rc[t] = 0;
    pool[s_tot ++] = t;
}

void _merge(int pr , int&nr) {
    if (!pr) return;
    if (!nr) nr = newnode();
    cnt[nr] += cnt[pr];
    if (cnt[lc[pr]]) _merge(lc[pr] , lc[nr]);
    if (cnt[rc[pr]]) _merge(rc[pr] , rc[nr]);
    delnode(pr);
}

int find(int u) { return u == fa[u] ? u : fa[u] = find(fa[u]); }

inline void merge(int u , int v) {
    u = find(u) , v = find(v);
    if (u == v) return ;
    if (rk[u] > rk[v]) swap(u , v);
    fa[u] = v;
    if (rk[u] == rk[v]) rk[v] ++;
    _merge(rt[u] , rt[v]);
    rt[u] = 0;
}

void update(int&u , int l , int r , int v) {
    if (!u) u = newnode();
    cnt[u] ++;
    if (l == r) return ;
    int m = (l + r) >> 1;
    if (v <= m)
        update(lc[u] , l , m , v);
    else
        update(rc[u] , m + 1 , r , v);
}

void input() {
    n = rd() , m = rd();
    rep (i , 1 , n) a[i] = rd();
    rep (i , 1 , n) h[a[i]] = i;
    rep (i , 1 , n) fa[i] = i;
    rep (i , 1 , n) rk[i] = 1;
    rep (i , 1 , n) update(rt[i] , 1 , n , a[i]);
    rep (i , 1 , m)
        merge(rd() , rd());
}

int kth(int u , int l , int r , int k) {
    int t = 0;
    if (cnt[u] < k) return -1;
    while (l < r) {
        int m = (l + r) >> 1;
        if (cnt[lc[u]] >= k)
            u = lc[u] , r = m;
        else
            k -= cnt[lc[u]] , u = rc[u] , l = m + 1;
    }
    return h[l];
}

void query(int u , int k) {
    u = find(u);
    int t = kth(rt[u] , 1 , n , k);
    printf("%d\n" , t);
}

void solve() {
    char cmd[2];
    rep (q , 1 , rd()) {
        scanf("%s" , cmd);
        int u = rd() , v = rd();
        if (cmd[0] == 'Q')
            query(u , v);
        else
            merge(u , v);
    }
}

int main() {
    #ifndef ONLINE_JUDGE
        freopen("data.txt" , "r" , stdin);
    // freopen("data.out" , "w" , stdout);
    #endif
    input();
    solve();
    return 0;
}