主席树 - 可持久化线段树

模板

P3834 【模板】可持久化线段树 2(主席树) 区间求第 \(k\) 大

模板代码

#include<bits/stdc++.h>
using namespace std;
#define Maxn 200005
typedef long long ll;
inline int rd()
{int x=0;char ch,t=0;while(!isdigit(ch = getchar())) t|=ch=='-';while(isdigit(ch)) x=x*10+(ch^48),ch=getchar();return x=t?-x:x;
}
/*
len: 数组长度
cnt: 数据范围 
*/
int len,n,m,used;
int root[Maxn],a[Maxn],True_val[Maxn];
struct Li
{int val,num;
}LI[Maxn];
bool cmp(Li x,Li y) { return x.val<y.val; }
struct Tree
{int ls,rs,sum;
}tree[Maxn<<5];
void pushup(int p)
{tree[p].sum=tree[tree[p].ls].sum+tree[tree[p].rs].sum;
}
void build(int p,int nl,int nr)
{if(nl==nr) return;int mid=(nl+nr)>>1;if(mid>=nl) tree[p].ls=++used,build(tree[p].ls,nl,mid);if(mid<nr) tree[p].rs=++used,build(tree[p].rs,mid+1,nr);
}
void add(int p1,int p2,int nl,int nr,int pos,int k)
{if(nl==nr) { tree[p2].sum=tree[p1].sum+k; return; }int mid=(nl+nr)>>1;tree[p2]=tree[p1];if(pos<=mid) tree[p2].ls=++used,add(tree[p1].ls,tree[p2].ls,nl,mid,pos,k);else tree[p2].rs=++used,add(tree[p1].rs,tree[p2].rs,mid+1,nr,pos,k);pushup(p2);
}
int query(int p1,int p2,int nl,int nr,int rank)
{if(nl==nr) return nl;int sumls=tree[tree[p2].ls].sum-tree[tree[p1].ls].sum,mid=(nl+nr)>>1;if(rank<=sumls) return query(tree[p1].ls,tree[p2].ls,nl,mid,rank);else return query(tree[p1].rs,tree[p2].rs,mid+1,nr,rank-sumls);
}
int main()
{//freopen(".in","r",stdin);//freopen(".out","w",stdout);len=rd(),m=rd();for(int i=1;i<=len;i++) LI[i].val=rd(),LI[i].num=i;sort(LI+1,LI+len+1,cmp),LI[0].val=-1;for(int i=1;i<=len;i++){if(LI[i].val!=LI[i-1].val) n++;a[LI[i].num]=n;True_val[n]=LI[i].val;}for(int i=0;i<=len;i++) root[i]=++used;build(root[0],1,n);for(int i=1;i<=len;i++) add(root[i-1],root[i],1,n,a[i],1);for(int i=1,l,r,k;i<=m;i++){l=rd(),r=rd(),k=rd();printf("%d\n",True_val[query(root[l-1],root[r],1,n,k)]);}//fclose(stdin);//fclose(stdout);return 0;
}