BZOJ 3224 普通平衡树

splay板子，记录一下

    #include <iostream>
    #include <cstdio>
    using namespace std;
    
    //define
    const int maxn=1e5+5;
    
    struct Splay{
        int ch[maxn<<1][2] ,par[maxn<<1] ,cnt[maxn<<1] ,size[maxn<<1] ,val[maxn<<1] ,ntot ,trt;
    
        int chk(int rt){return ch[par[rt]][1] == rt;}
    
        void pushup(int rt){size[rt] = size[ch[rt][0]] + size[ch[rt][1]] + cnt[rt];}
    
        void rotate(int rt){
            int y = par[rt];
            int z = par[y];
            int rnk = chk(rt);
            int w = ch[rt][rnk^1];
            ch[y][rnk] = w; par[w] = y;
            ch[z][chk(y)] = rt;par[rt] = z;
            ch[rt][rnk^1] = y;par[y] = rt;
            pushup(y); pushup(rt);
        }
    
        void splay(int rt,int g = 0){
            while(par[rt] != g){
                int y = par[rt] ,z = par[y];
                if(z != g){
                    if(chk(rt) == chk(y))rotate(y);
                    else rotate(rt);
                }
                rotate(rt);
            }
            if(!g) trt = rt;
        }
    
        void find(int rt){
            if(!trt) return ;
            int cur = trt;
            while(ch[cur][rt > val[cur]] && rt != val[cur]){
                cur = ch[cur][rt > val[cur]];
            }
            splay(cur);
        }
    
        void insert(int rt){
            int cur = trt ,p = 0;
            while(cur && val[cur] != rt){
                p = cur;
                cur = ch[cur][rt > val[cur]];
            }
            if(cur){
                cnt[cur]++;
            }
            else{
                cur = ++ntot;
                if(p) ch[p][rt > val[p]] = cur;
                ch[cur][0] = ch[cur][1] = 0;
                val[cur] = rt;
                par[cur] = p;
                cnt[cur] = size[cur] = 1;
            }
            splay(cur);
        }
    
        int kth(int k){
            int cur = trt;
            while(1){
                if(ch[cur][0] && k <= size[ch[cur][0]]){
                    cur = ch[cur][0];
                }
                else if(k > size[ch[cur][0]] + cnt[cur]){
                    k -= size[ch[cur][0]] + cnt[cur];
                    cur = ch[cur][1];
                }
                else{
                    return cur;
                }
            }
        }
    
        int pre(int rt){
            find(rt);
            if(val[trt] < rt)return trt;
            int cur = ch[trt][0];
            while(ch[cur][1]) cur = ch[cur][1];
            return cur;
        }
    
        int src(int rt){
            find(rt);
            if(val[trt] > rt)return trt;
            int cur = ch[trt][1];
            while(ch[cur][0]) cur = ch[cur][0];
            return cur;
        }
    
        void remove(int rt){
            int last = pre(rt) ,next = src(rt);
            splay(last); splay(next ,last);
            int del = ch[next][0];
            if(cnt[del] > 1){
                cnt[del]--;
                splay(del);
            }
            else ch[next][0] = 0;
        }
    
        int get_rt(){
            return size[ch[trt][0]];
        }
    
        int get_kth(int rt){
            return val[kth(rt+1)];
        }
    
        int get_pre(int rt){
            return val[pre(rt)];
        }
    
        int get_src(int rt){
            return val[src(rt)];
        }
    }tree;
    
    //main
    int main(){
        ios::sync_with_stdio(false);
        int n,op,x;
        cin>>n;
        tree.insert(0x3f3f3f3f);
        tree.insert(0xcfcfcfcf);
        while(n--){
            cin>>op>>x;
            if(op == 1){
                tree.insert(x);
            }
            if(op == 2){
                tree.remove(x);
            }
            if(op == 3){
                tree.find(x);
                cout<<tree.get_rt()<<endl;
            }
            if(op == 4){
                cout<<tree.get_kth(x)<<endl;
            }
            if(op == 5){
                cout<<tree.get_pre(x)<<endl;
            }
            if(op == 6){
                cout<<tree.get_src(x)<<endl;
            }
        }
        return 0;
    }