luogu1486 [NOI2004]郁闷的出纳员 （平衡树）

加的注释，都流着泪。。。
胡了一种做法，样例都没过，翻题解发现一神仙Remove操作，妙啊！

#include <iostream>
#include <cstdio>
#include <cstring>
#include <algorithm>
#include <cmath>
#define R(a,b,c) for(register int  a = (b); a <= (c); ++ a)
#define nR(a,b,c) for(register int  a = (b); a >= (c); -- a)
#define Max(a,b) ((a) > (b) ? (a) : (b))
#define Min(a,b) ((a) < (b) ? (a) : (b))
#define Fill(a,b) memset(a, b, sizeof(a))
#define Abs(a) ((a) < 0 ? -(a) : (a))
#define Swap(a,b) a^=b^=a^=b
#define ll long long

#define ON_DEBUG

#ifdef ON_DEBUG

#define D_e_Line printf("

----------

")
#define D_e(x)  cout << #x << " = " << x << endl
#define Pause() system("pause")
#define FileOpen() freopen("in.txt","r",stdin);

#else

#define D_e_Line ;
#define D_e(x)  ;
#define Pause() ;
#define FileOpen() ;

#endif

struct ios{
    template<typename ATP>ios& operator >> (ATP &x){
        x = 0; int f = 1; char c;
        for(c = getchar(); c < '0' || c > '9'; c = getchar()) if(c == '-')  f = -1;
        while(c >= '0' && c <= '9') x = x * 10 + (c ^ '0'), c = getchar();
        x*= f;
        return *this;
    }
}io;
using namespace std;

const int N = 100007;

int minLimit, totLeave;
struct Treap{
	int ch[2], fa, val, tot, siz;
}t[N];
int root, treeIndex;
inline void Pushup(int rt){
	t[rt].siz = t[t[rt].ch[0]].siz + t[t[rt].ch[1]].siz + t[rt].tot;
}
inline int Ident(int x){
	return t[t[x].fa].ch[1] == x;
}
inline void Rotate(int x){
	int y = t[x].fa, z = t[y].fa, k = Ident(x);
	t[z].ch[Ident(y)] = x, t[x].fa = z;
	t[y].ch[k] = t[x].ch[k ^ 1], t[t[x].ch[k ^ 1]].fa = y;
	t[x].ch[k ^ 1] = y, t[y].fa = x;
	Pushup(y), Pushup(x);
}
inline void Splay(int x, int pos){
	while(t[x].fa != pos){
		int y = t[x].fa, z = t[y].fa;
		if(z != pos){
			Ident(x) == Ident(y) ? Rotate(y) : Rotate(x);
		}
		Rotate(x);
	}
	if(!pos) root = x;
}
inline void Insert(int x){
	if(x < minLimit) return;
	int u = root, fa = 0;
	while(u && t[u].val != x){ // !
		fa = u;
		u = t[u].ch[x > t[u].val];
	}
	if(u){
		++t[u].tot;
	}
	else{
		u = ++treeIndex;
		t[u].ch[0] = t[u].ch[1] = 0;
		t[u].siz = t[u].tot = 1;
		t[u].fa = fa;
		t[u].val = x;
		if(fa) t[fa].ch[x > t[fa].val] = u;
	}
	Splay(u, 0);
}
inline void Find(int x){
	int u = root;
	if(!u) return;
	while(t[u].val != x && t[u].ch[x > t[u].val]) u = t[u].ch[x > t[u].val]; // !
	Splay(u, 0); // !
	return;
}
inline void Add(int x){
	R(i,1,treeIndex) t[i].val += x;
}
inline void Sub(int x){
	R(i,1,treeIndex) t[i].val -= x;
}

inline int Next(int x, int type){ // the minimu number >= x
	Find(x);
	int u = root;
	if((t[u].val >= x && type) || (t[u].val < x && !type)) return u; // >= ?
	u = t[u].ch[type];
	while(t[u].ch[type ^ 1]) u = t[u].ch[type ^ 1];
	return u;
}

inline void Remove(int x){ // %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
    int rt = Next(x + minLimit, 1);
    Splay(rt, 0);
    totLeave += t[t[rt].ch[0]].siz;
    t[rt].ch[0] = 0;
    Pushup(rt);
    Sub(x);
}

inline int Kth(int x){
	int u = root;
	if(t[u].siz <= x) return -1;
	++x;
	while(1){
		int v = t[u].ch[1];
		if(t[v].siz + t[u].tot < x){
			x -= t[v].siz + t[u].tot;
			u = t[u].ch[0];
		}
		else if(x <= t[v].siz){ // !
			u = v;
		}
		else
			return t[u].val;
	}
}

int main(){
//FileOpen();
//freopen("my.txt","w",stdout);
	int m;
    io >> m >> minLimit;
	Insert(2147483647);
//	Insert(-2147483647);
    while(m --){
		char opt = getchar();
		while(opt != 'I' && opt != 'S' && opt != 'A' && opt != 'F') opt = getchar();
		int x;
        io >> x;
        if(opt == 'I'){
        	Insert(x);
        }
        else if(opt == 'A'){
        	Add(x);
        }
        else if(opt == 'S'){
        	Remove(x);
        }
        else{
        	printf("%d
",Kth(x));
        }
    }
    
    printf("%d", totLeave);
    return 0;
}