题面
解析
线段树和Splay两棵树套在一起，常数直逼inf，但最终侥幸过了
思路还是比较简单， 在原数组维护一个下标线段树，再在每一个线段树节点，维护一个对应区间的权值Splay。简单说一下操作：
0.提取区间
这个操作是1、2、4、5操作的基础，其实也比较容易实现，在线段树中跑一跑，如果询问区间包含了节点覆盖的区间，就在一个数组中存一下节点的编号，然后返回就行
1.查询区间内k的排名
提取区间，找到区间内所有的Splay， 分别比k小的数的个数，相加后加一即可
2.查询区间第k大
提取区间，找到区间内所有的Splay，因为有多棵Splay，这个操作显然不能像一般的Splay一样查询，只能二分答案，转化为操作一，再check排名就行
3.单点修改
先在线段树中向下找到包含pos的所有节点，将这些节点对应的Splay中原值删去， 加入新值即可
4.求前驱
同样找到区间内的所有Splay，分别进入找前驱，输出最大的前驱即可。但k可能不在Splay中，于是我们先要找到大于等于k的权值最小的节点，将它旋转到根，再找前驱，但由于可能没有前驱，就在每棵Splay插入-inf， 查询排名时记得减去即可
5.求后继
操作与前驱类似，找到小于等于k的权值最大的节点，旋转到根，找后继，记得每棵Splay插入inf就行
大部分操作都是自己YY的，可能不是很优秀，但我这个又臭又长的代码并没有调试多久，也是不容易啊。
代码（340行）：
#includeusing namespace std;const int maxn = 100005, inf = 2147483647;template void read(T &re){ re=0; T sign=1; char tmp; while((tmp=getchar())&&(tmp<'0'||tmp>'9')) if(tmp=='-') sign=-1; re=tmp-'0'; while((tmp=getchar())&&(tmp>='0'&&tmp<='9')) re=(re<<3)+(re<<1)+(tmp-'0'); re*=sign;}int n, m, root[maxn<<1], rt, a[maxn];int tot, cnt, lson[maxn<<1], rson[maxn<<1], stak[maxn], top, s[maxn], snum;struct Splay_tree{ int fa, s[2], val, siz, num;}tr[maxn * 20];void update(int x){ int ls = tr[x].s[0], rs = tr[x].s[1]; tr[x].siz = tr[ls].siz + tr[rs].siz + tr[x].num;}void Rotate(int x){ int y = tr[x].fa, z = tr[y].fa, k = (tr[y].s[1] == x), w = (tr[z].s[1] == y), son = tr[x].s[k^1]; tr[y].s[k] = son;tr[son].fa = y; tr[x].s[k^1] = y;tr[y].fa = x; tr[z].s[w] = x;tr[x].fa = z; update(y);update(x);}void Splay(int x, int to, int id){ int y, z; while(tr[x].fa != to) { y = tr[x].fa;z = tr[y].fa; if(z != to) Rotate((tr[y].s[0] == x) ^ (tr[z].s[0] == y)? x: y); Rotate(x); } if(!to) root[id] = x;}void Insert(int x, int v){ int now = root[x], ff = 0; while(now) { ff = now; tr[now].siz ++; if(tr[now].val == v) break; now = tr[now].s[v>tr[now].val]; } if(now) tr[now].num ++; else { if(snum) now = s[snum--]; else now = ++cnt; tr[now].val = v; tr[ff].s[v>tr[ff].val] = now; tr[now].fa = ff; tr[now].num = 1; tr[now].siz = 1; tr[now].s[0] = tr[now].s[1] = 0; } Splay(now, 0, x);}void build(int &x, int l, int r){ x = ++tot; root[x] = ++cnt; tr[root[x]].val = -inf; tr[root[x]].siz = tr[root[x]].num = 1; tr[0].s[1] = root[x]; Insert(x, inf); for(int i = l; i <= r; ++i) Insert(x, a[i]); if(l == r) return ; int mid = (l + r)>>1; build(lson[x], l, mid); build(rson[x], mid + 1, r); }void Extract(int x, int l, int r, int L, int R){ if(l <= L && R <= r) { stak[++top] = x; return ; } int mid = (L + R)>>1; if(l <= mid) Extract(lson[x], l, r, L, mid); if(mid < r) Extract(rson[x], l, r, mid + 1, R);}int Queryrk(int id, int x){ int now = root[id], ret = 0; while(now) { int ls = tr[now].s[0], rs = tr[now].s[1]; if(x < tr[now].val) { if(ls) now = ls; else break; } else if(x == tr[now].val) { ret += tr[ls].siz ; break; } else { ret += tr[ls].siz + tr[now].num; if(rs) now = rs; else break; } } tr[0].s[1] = root[id]; Splay(now, 0, id); return ret;}int work1(int x){ int ret = -top; while(top) { ret += Queryrk(stak[top], x); top --; } return ret + 1;}int check(int x){ int ret = 0; for(int i = 1; i <= top; ++i) ret += Queryrk(stak[i], x); return ret + 1;}int work2(int x){ x += top; int l = 0, r = 1e8, mid, ret = 0; while(l <= r) { mid = (l + r)>>1; if(check(mid) <= x) ret = mid, l = mid + 1; else r = mid - 1; } top = 0; return ret;}int Find(int now, int x){ while(1) { int ls = tr[now].s[0], rs = tr[now].s[1]; if(tr[now].val == x) return now; if(x < tr[now].val) now = ls; else now = rs; }}int Querypre(int now){ now = tr[now].s[0]; while(tr[now].s[1]) now = tr[now].s[1]; return now;}int Querynxt(int now){ now = tr[now].s[1]; while(tr[now].s[0]) now = tr[now].s[0]; return now;}void Modify(int x, int pos, int l, int r, int v){ tr[0].s[1] = root[x]; int y = Find(root[x], a[pos]); Splay(y, 0, x); int pre = Querypre(root[x]); int nxt = Querynxt(root[x]); Splay(pre, 0, x);Splay(nxt, pre, x); if(tr[y].num > 1) { tr[y].num --; tr[y].siz --; } else { s[++snum] = y; tr[nxt].s[0] = 0; } update(nxt);update(pre); Insert(x, v); if(l == r) { a[pos] = v; return ; } int mid = (l + r)>>1; if(pos <= mid) Modify(lson[x], pos, l, mid, v); else Modify(rson[x], pos, mid + 1, r, v);}int Findmx(int now, int x){ int ret = 0; while(now) { int ls = tr[now].s[0], rs = tr[now].s[1]; if(tr[now].val == x) return now; if(tr[now].val > x) { ret = now; now = ls; } else now = rs; } return ret;}int Findmn(int now, int x){ int ret = 0; while(now) { int ls = tr[now].s[0], rs = tr[now].s[1]; if(tr[now].val == x) return now; if(tr[now].val < x) { ret = now; now = rs; } else now = ls; } return ret;}int work3(int x){ int ret = -inf; while(top) { tr[0].s[1] = root[stak[top]]; int now = Findmx(root[stak[top]], x); Splay(now, 0, stak[top]); int pre = Querypre(root[stak[top]]); ret = max(ret, tr[pre].val); top--; } return ret;}int work4(int x){ int ret = inf; while(top) { tr[0].s[1] = root[stak[top]]; int now = Findmn(root[stak[top]], x); Splay(now, 0, stak[top]); int nxt = Querynxt(root[stak[top]]); ret = min(ret, tr[nxt].val); top--; } return ret;}int main(){ read(n);read(m); for(int i = 1; i <= n; ++i) read(a[i]); build(rt, 1, n); for(int i = 1; i <= m; ++i) { int opt, l, r, k, pos; read(opt); if(opt == 1) { read(l);read(r);read(k); Extract(rt, l, r, 1, n); printf("%d\n", work1(k)); } else if(opt == 2) { read(l);read(r);read(k); Extract(rt, l, r, 1, n); printf("%d\n", work2(k)); } else if(opt == 3) { read(pos);read(k); Modify(rt, pos, 1, n, k); } else if(opt == 4) { read(l);read(r);read(k); Extract(rt, l, r, 1, n); printf("%d\n", work3(k)); } else { read(l);read(r);read(k); Extract(rt, l, r, 1, n); printf("%d\n", work4(k)); } } return 0;}