学步园

http://www.lydsy.com/JudgeOnline/problem.php?id=1503

都是些基本的平衡树操作，各种平衡树都可以，我用的splay

//插入，删除（一棵子树），找第k大
#include<cstdio>
const int inf  = ~0u>>2;
#define KT (ch[ ch[rt][1] ][0])
const int maxn = 200010;
int lim;
struct SplayTree {
    int sz[maxn];
    int ch[maxn][2];
    int pre[maxn];
    int rt,top;
    inline void up(int x){
        sz[x]  = cnt[x]  + sz[ ch[x][0] ] + sz[ ch[x][1] ];
    }
    inline void Rotate(int x,int f){
        int y=pre[x];
        ch[y][!f] = ch[x][f];
        pre[ ch[x][f] ] = y;
        pre[x] = pre[y];
        if(pre[x]) ch[ pre[y] ][ ch[pre[y]][1] == y ] =x;
        ch[x][f] = y;
        pre[y] = x;
        up(y);
    }
    inline void Splay(int x,int goal){//将x旋转到goal的下面
        while(pre[x] != goal){
            if(pre[pre[x]] == goal) Rotate(x , ch[pre[x]][0] == x);
            else   {
                int y=pre[x],z=pre[y];
                int f = (ch[z][0]==y);
                if(ch[y][f] == x) Rotate(x,!f),Rotate(x,f);
                else Rotate(y,f),Rotate(x,f);
            }
        }
        up(x);
        if(goal==0) rt=x;
    }
    inline void RTO(int k,int goal){//将第k位数旋转到goal的下面
        int x=rt;
        while(sz[ ch[x][0] ] != k-1) {
            if(k < sz[ ch[x][0] ]+1) x=ch[x][0];
            else {
                k-=(sz[ ch[x][0] ]+1);
                x = ch[x][1];
            }
        }
        Splay(x,goal);
    }
    inline void vist(int x){
        if(x){
            printf("结点%2d : 左儿子  %2d   右儿子  %2d   %2d sz=%d\n",x,ch[x][0],ch[x][1],val[x],sz[x]);
            vist(ch[x][0]);
            vist(ch[x][1]);
        }
    }
    inline void Newnode(int &x,int c){
        x=++top;
        ch[x][0] = ch[x][1] = pre[x] = 0;
        sz[x]=1; cnt[x]=1;
        val[x] = c;
    }
    inline void init(){
        sum=ch[0][0]=ch[0][1]=pre[0]=sz[0]=0;
        rt=top=0; cnt[0]=0;
    }
    inline void Insert(int &x,int key,int f){
        if(!x) {
            Newnode(x,key);
            pre[x]=f;
            Splay(x,0);
            return ;
        }
        if(key==val[x]){
            cnt[x]++;
            sz[x]++;
            Splay(x,0);
            return ;
        }else if(key<val[x]) {
            Insert(ch[x][0],key,x);
        } else {
            Insert(ch[x][1],key,x);
        }
        up(x);
    }
    void del(int &x,int f){
        if(!x) return ;
        if(val[x]>=lim){
            del(ch[x][0],x);
        } else {
            sum+=sz[ch[x][0]]+cnt[x];
            x=ch[x][1]; 
            pre[x]=f;
            if(f==0) rt=x;
            del(x,f);
        }
        if(x)  up(x);
    }
    inline void update(){
        del(rt,0);
    }
    inline int find_kth(int x,int k){
        if(k<sz[ch[x][0]]+1) {
            return find_kth(ch[x][0],k);
        }else if(k > sz[ ch[x][0] ] + cnt[x] ) 
            return find_kth(ch[x][1],k-sz[ch[x][0]]-cnt[x]);
        else{ 
            Splay(x,0);
            return val[x];
        }
    }
    int cnt[maxn];
    int val[maxn];
    int sum;
}spt;
int main(){
    int n;
    char op[5];
    scanf("%d%d",&n,&lim);
    int lim0=lim;
    spt.init();
    while(n--){
        int k;
        scanf("%s%d",op,&k);
        if(op[0]=='I'){
            if(k<lim0) {continue;}
            spt.Insert(spt.rt,k+lim-lim0,0);
        } else if(op[0]=='A'){
            lim-=k;
        }else if(op[0]=='S'){
            lim+=k;
            if(spt.sz[spt.rt]>0) spt.update();
        } else {
            int sz=spt.sz[spt.rt];
            if(k>sz) printf("-1\n");
            else {
                printf("%d\n",spt.find_kth(spt.rt,sz-k+1)-lim+lim0);
            }
        }   
       // spt.vist(spt.rt);
    }
    printf("%d\n",spt.sum);
    return 0;
}