Bandit fhq-treap

Bandit fhq-treap

Face questions

Observation topic found that the available balance of the tree do: Devils pushers each node that is removed from the balance added to the tree; every time the villagers repair the house to remove the node to balance the tree; each query, simply requires a subsequent drive and precursors, easy to know nxt-pre-1is the answer.

Use \ (\ text {fhq-treap } \) balanced tree portion

#include <cstdio>
#include <cstdlib>
#define MAXN 50005
using namespace std;
struct nod{
    int sl,sr,val,rnd,sz;
} tre[MAXN];
void update(int x){
    tre[x].sz=1+tre[tre[x].sl].sz+tre[tre[x].sr].sz;
}
int merge(int x, int y){
    if(x==0||y==0) return x|y;
    if(tre[x].rnd<tre[y].rnd){
        tre[x].sr=merge(tre[x].sr, y);
        update(x);
        return x;
    }else{
        tre[y].sl=merge(x, tre[y].sl);
        update(y);
        return y;
    }
}
void split(int cur, int k, int &x, int &y){
    if(cur==0){x=y=0; return;}
    if(tre[cur].val<=k){
        x=cur;
        split(tre[cur].sr, k, tre[cur].sr, y);
    }else{
        y=cur;
        split(tre[cur].sl, k, x, tre[cur].sl);
    }
    update(cur);
}
int tot,rot,x,y,z;
int new_nod(int val){
    tre[++tot].val=val;
    tre[tot].sz=1;
    tre[tot].rnd=rand();
    return tot;
}
void add(int val){
    split(rot, val, x, y);
    rot=merge(merge(x, new_nod(val)), y);
}
void del(int val){
    split(rot, val, x, z);
    split(x, val-1, x, y);
    y=merge(tre[y].sl, tre[y].sr);
    rot=merge(merge(x, y), z);
}
int get_kth(int cur, int k){
    while(1){
        if(k<=tre[tre[cur].sl].sz) cur=tre[cur].sl;
        else if(k==tre[tre[cur].sl].sz+1) return cur;
        else k-=tre[tre[cur].sl].sz+1, cur=tre[cur].sr;
    }
}
int get_pre(int val){
    split(rot, val-1, x, y);
    int res=get_kth(x, tre[x].sz);
    rot=merge(x,y);
    return res;
}
int get_nxt(int val){
    split(rot, val, x, y);
    int res=get_kth(y, 1);
    rot=merge(x,y);
    return res;
}
int n,m;
int s[MAXN],top;
bool des[MAXN];
int main(){
    srand((unsigned)19270817);
    scanf("%d %d", &n, &m);
    add(0),add(n+1);
    while(m--){
        char opt;int t;
        scanf("\n%c ", &opt);
        if(opt=='D'){
            scanf("%d", &t);
            add(t);
            s[++top]=t;
            des[t]=1;
        }else if(opt=='Q'){
            scanf("%d", &t);
            if(des[t]) printf("0\n");
            else printf("%d\n", tre[get_nxt(t)].val-tre[get_pre(t)].val-1);
        }else if(opt=='R'){
            while(des[s[top]]==0) ++top;
            des[s[top]]=0;
            del(s[top--]);
        }else puts("Erro!");
    }
    return 0;
}