【luoguP1533】可怜的狗狗

题目链接

发现区间按左端点排序后右端点也是单调的，所以扫一遍就行了，用权值线段树维护第\(k\)大

#include<algorithm>
#include<iostream>
#include<cstring>
#include<cstdio>
#include<map>
#define int long long
#define lc (p<<1)
#define rc (p<<1|1)
using namespace std;

const int MAXN=2000010;
const int MAXM=500010;

inline int read(){
	int x=0,f=1; char c=getchar();
	while(c<'0'){ if(c=='-') f=-1; c=getchar(); }
	while(c>='0') x=x*10+c-'0',c=getchar();
	return x*f;
}

int n,m,a[MAXN],t[MAXN],cnt,num;

struct Query{
	int l,r,k,id;
} q[MAXM];

inline bool cmp(Query x,Query y){
	return x.l<y.l;
}

map<int,int> Map;
int rev[MAXN];

int tree[MAXN];
inline void update(int k,int d,int p=1,int l=1,int r=num){
	if(l==r){
		tree[p]+=d;
		return;
	}
	int mid=(l+r)>>1;
	if(k<=mid) update(k,d,lc,l,mid);
	else update(k,d,rc,mid+1,r);
	tree[p]=tree[lc]+tree[rc];
}

inline int query(int k,int p=1,int l=1,int r=num){
	if(l==r) return l;
	int mid=(l+r)>>1;
	if(tree[lc]>=k) return query(k,lc,l,mid);
	else return query(k-tree[lc],rc,mid+1,r);
}

int ans[MAXN];

signed main(){
	n=read(); m=read();
	for(int i=1;i<=n;++i)
		a[i]=read(),t[++cnt]=a[i];
	for(int i=1;i<=m;++i)
		q[i].l=read(),q[i].r=read(),q[i].k=read(),q[i].id=i;
	sort(q+1,q+1+m,cmp);
	sort(t+1,t+1+cnt);
	t[0]=t[1]-1;
	for(int i=1;i<=cnt;++i)
		if(t[i]!=t[i-1]) Map[t[i]]=++num,rev[num]=t[i];
	int L=1,R=0;
	for(int i=1;i<=m;++i){
		while(R<q[i].r) update(Map[a[++R]],1);
		while(L<q[i].l) update(Map[a[L++]],-1);
		ans[q[i].id]=rev[query(q[i].k)];
	}
	for(int i=1;i<=m;++i)
		printf("%lld\n",ans[i]);
	return 0;
}