主席树套树状数组 动态区间第k小

先打上代码以后更新解释

#include <cstdio>
#include <iostream>
#include <algorithm>
#include <cstring>
#include <cmath>
#define REP(i, s, n) for(int i = s; i <= n; i ++)
#define RAP(i, n, s) for(int i = n; i >= s; i --)
#define LOW for(; x; x -= x & (-x))
using namespace std;
const int maxn = 100000 + 10;
const int Maxn = 100000;
const int maxnode = 200 * maxn;
int s[maxnode], ls[maxnode], rs[maxnode], A[maxn], root[maxn], Ln, Rn, L[maxn], R[maxn], c[maxn];
int n, Q, ms = 0;
void update(int x, int& y, int L, int R, int pos, int v){
    s[y = ++ ms] = s[x] + v;
    if(L == R) return ;
    int M = L + R >> 1;
    ls[y] = ls[x]; rs[y] = rs[x];
    if(pos <= M) update(ls[x], ls[y], L, M, pos, v);
    else update(rs[x], rs[y], M + 1, R, pos, v);
    return ;
}
void update(int x, int v){
    for(int i = x; i <= Maxn; i += i & (-i)) update(c[i], c[i], 1, Maxn, A[x], -1); A[x] = v;
    for(int i = x; i <= Maxn; i += i & (-i)) update(c[i], c[i], 1, Maxn, A[x], 1); return ;
}
void init(int x, int tp){
    if(!tp) { L[++ Ln] = root[x]; LOW if(c[x]) L[++ Ln] = c[x]; }
    else { R[++ Rn] = root[x]; LOW if(c[x]) R[++ Rn] = c[x]; }
    return ;
}
int query(int ql, int qr, int k){
    Ln = Rn = 0; init(qr, 1); init(ql - 1, 0);//0是左
    int ll = 1, rr = Maxn;
    while(ll < rr){
        int Lsum = 0, Rsum = 0, M = ll + rr >> 1;
        REP(i, 1, Ln) Lsum += s[ls[L[i]]];
        REP(i, 1, Rn) Rsum += s[ls[R[i]]];
        int kth = Rsum - Lsum;
        if(kth >= k){//往左找 
            REP(i, 1, Ln) L[i] = ls[L[i]];
            REP(i, 1, Rn) R[i] = ls[R[i]];
            rr = M;
        }
        else{//往右找 
            REP(i, 1, Ln) L[i] = rs[L[i]];
            REP(i, 1, Rn) R[i] = rs[R[i]];
            ll = M + 1; k -= kth; //看好了二分！ 别忘了还要减 Σ( ° △ °|||)︴ 
        }
    }
    return ll;
}
inline void read(int &x){
    x = 0; int sig = 1; char ch = getchar();
    while(!isdigit(ch)) { if(ch == '-') sig = -1; ch = getchar(); }
    while(isdigit(ch)) x = 10 * x + ch - '0', ch = getchar();
    x *= sig; return ;
}
inline void write(int x){
    if(x == 0) { putchar('0'); return ; }
    if(x < 0) putchar('-'), x = -x;
    int len = 0, buf[20];
    while(x) buf[len ++] = x % 10, x /= 10;
    RAP(i, len - 1, 0) putchar(buf[i] + '0'); return ;
}
void init(){
    read(n); read(Q);
    REP(i, 1, n) read(A[i]);
    REP(i, 1, n) update(root[i - 1], root[i], 1, Maxn, A[i], 1);
    return ;
}
void work(){
    int tp, ql, qr, k, x, v;
    while(Q --){
        read(tp);
        if(tp) read(ql), read(qr), read(k), write(query(ql, qr, k) - 1), putchar('\n');// 减一 
        else read(x), read(v), update(x, v);
    }
    return ;
}
void print(){

    return ;
}
int main(){
    init();
    work();
    print();
    return 0;
}

 逗比版：

#include<iostream>
#include<cstdio>
#include<cmath>
#include<algorithm>
#define t node[d]
#define cnt countn[d]
#define repnode(d) for(int i=1;i<=countn[d];i++)
using namespace std;
const int maxn=100000+10,maxnode=20000000+10,Max=100000;
int ls[maxnode],rs[maxnode],s[maxnode],root[maxn],A[maxn],c[maxn],n,m,ms=0,countn[2],node[2][maxn],sum[2];
void update(int x,int& y,int L,int R,int pos,int d){
    s[y=++ms]=s[x]+d;
    if(L==R) return;
    ls[y]=ls[x];rs[y]=rs[x];
    int M=L+R>>1;
    if(pos<=M) update(ls[x],ls[y],L,M,pos,d);
    else update(rs[x],rs[y],M+1,R,pos,d);
    return;
}
void update(int x,int v){
    for(int i=x;i<=Max;i+=i&-i) update(c[i],c[i],1,Max,A[x],-1);A[x]=v;
    for(int i=x;i<=Max;i+=i&-i) update(c[i],c[i],1,Max,A[x],1);return;
}
void init(int x,int d){
    t[++cnt]=root[x];
    for(;x;x-=x&-x) if(c[x]) t[++cnt]=c[x];
    return;
}
int query(int ql,int qr,int k){
    countn[0]=countn[1]=0;
    init(qr,1);init(ql-1,0);
    int L=1,R=Max,d;
    while(L<R){
        sum[0]=sum[1]=0;
        int M=L+R>>1;
        repnode(d=0) sum[d]+=s[ls[t[i]]];
        repnode(d=1) sum[d]+=s[ls[t[i]]];
        int kth=sum[1]-sum[0];
        if(k<=kth){
            repnode(d=0) t[i]=ls[t[i]];
            repnode(d=1) t[i]=ls[t[i]];
            R=M;
        }
        else{
            repnode(d=0) t[i]=rs[t[i]];
            repnode(d=1) t[i]=rs[t[i]];
            L=M+1;k-=kth;
        }
    } return L;
}
inline int read(){
    int x=0,sig=1;char ch=getchar();
    while(!isdigit(ch)){if(ch=='-') sig=-1;ch=getchar();}
    while(isdigit(ch)) x=10*x+ch-'0',ch=getchar();
    return x*=sig;
}
inline void write(int x){
    if(x==0){putchar('0');return;} if(x<0) putchar('-'),x=-x;
    int len=0,buf[15]; while(x) buf[len++]=x%10,x/=10;
    for(int i=len-1;i>=0;i--) putchar(buf[i]+'0');return;
}
void init(){
    n=read();m=read();
    for(int i=1;i<=n;i++) A[i]=read();
    for(int i=1;i<=n;i++) update(root[i-1],root[i],1,Max,A[i],1);
    return;
}
void work(){
    int tp,i,j,k,x,v;
    while(m--){
        tp=read();
        if(tp){
            i=read();j=read();k=read();
            write(query(i,j,k)-1);putchar('\n');
        }
        else{
            x=read();v=read();
            update(x,v);
        }
    }
    return;
}
void print(){
    return;
}
int main(){
    init();work();print();return 0;
}