洛谷P3871 [TJOI2010]中位数(splay)

6
1 2 13 14 15 16
5
add 5
add 3
mid
add 20
mid

5
13

#include<cstdio>
using namespace std;
const int MAXN = 1e6 + 10;
#define ls(x) ch[x][0]
#define rs(x) ch[x][1]
#define root  ch[0][1]
int fa[MAXN], val[MAXN], rev[MAXN], siz[MAXN], ch[MAXN][2], tot = 0;
bool ident(int x) {
    return ch[fa[x]][0] == x ? 0 : 1;
}
void connect(int x, int _fa, int opt) {
    fa[x] = _fa, ch[fa[x]][opt] = x;
}
void update(int x) {
    siz[x] = siz[ls(x)] + siz[rs(x)] + rev[x];
}
void rotate(int x) {
    int Y = fa[x], R = fa[Y];
    int Yson = ident(x), Rson = ident(Y);
    int B = ch[x][Yson ^ 1];
    connect(B, Y, Yson);
    connect(x, R, Rson);
    connect(Y, x, Yson ^ 1);
    //tag 
    update(Y); update(x);
}
void splay(int x, int to) {
    to = fa[to]; 
    while(fa[x] != to) {
        int y = fa[x];
        if(fa[y] == to) rotate(x); 
        else if(ident(x) == ident(y)) rotate(y), rotate(x);
        else rotate(x), rotate(x);
    }
}
int NewNode(int _fa, int _val) {
    val[++tot] = _val;
    fa[tot] = _fa;
    siz[tot] = rev[tot] = 1;
    return tot;
}
void insert(int x) {
    if(!root) {root = NewNode(0, x); return ;}
    int now = root;
    while(now) {
        siz[now]++;
        if(val[now] == x) {rev[now]++; return ;}
        int nxt = val[now] < x;
        if(!ch[now][nxt]) {ch[now][nxt] = NewNode(now, x); splay(ch[now][nxt], root); return ;}
        now = ch[now][nxt];
    }
}
int ARank(int x) {
    int now = root;
    while(now) {
        //if(siz[now] == x) return val[now];
        int used = siz[now] - siz[rs(now)];
        if(x > siz[ls(now)] && x <= used) return val[now];
        if(used < x) x = x - used, now = ch[now][1];
        else now = ch[now][0];
    }
}
char opt[5];
int main() {
#ifdef WIN32
    freopen("a.in", "r", stdin);
#endif
    int N;
    scanf("%d", &N);
    for(int i = 1; i <= N; i++) {
        int x; scanf("%d", &x);
        insert(x);
    }
    int Q;
    scanf("%d", &Q);
    while(Q--) {
        scanf("%s", opt + 1);
        if(opt[1] == 'a') {
            int x;
            scanf("%d", &x);
            insert(x); N++;    
        }
        else 
            printf("%d\n", ARank(N / 2 + (N & 1)));
    }
    return 0;
}