BZOJ3524 & LOJ2432：[POI2014]代理商Couriers——题解

https://www.lydsy.com/JudgeOnline/problem.php?id=3524

https://loj.ac/problem/2432

水一发题解，重题：BZOJ2223：[Coci2009]PATULJCI

#include<cstdio>
#include<queue>
#include<cctype>
#include<cstring>
#include<cmath>
#include<vector>
#include<algorithm>
using namespace std;
const int N=5e5+5;
inline int read(){
int X=0,w=0;char ch=0;
while(!isdigit(ch)){w|=ch=='-';ch=getchar();}
while(isdigit(ch))X=(X<<3)+(X<<1)+(ch^48),ch=getchar();
return w?-X:X;
}
struct tree{
int l,r,sum;
}tr[N*25];
int rt
,n,m,q,pool;
inline void insert(int &y,int &x,int l,int r,int p){
tr[x=++pool]=tr[y];
tr[x].sum++;
if(l==r)return;
int mid=(l+r)>>1;
if(p<=mid)insert(tr[y].l,tr[x].l,l,mid,p);
else insert(tr[y].r,tr[x].r,mid+1,r,p);
return;
}
inline int query(int nl,int nr,int l,int r,int k){
if(l==r)return l;
int d1=tr[tr[nr].l].sum-tr[tr[nl].l].sum;
int d2=tr[tr[nr].r].sum-tr[tr[nl].r].sum;
int mid=(l+r)>>1;
if(d1>k)return query(tr[nl].l,tr[nr].l,l,mid,k);
if(d2>k)return query(tr[nl].r,tr[nr].r,mid+1,r,k);
return 0;
}
int main(){
n=read();q=read();
for(int i=1;i<=n;i++)insert(rt[i-1],rt[i],1,n,read());
for(int i=1;i<=q;i++){
int l=read(),r=read();
int ans=query(rt[l-1],rt[r],1,n,(r-l+1)>>1);
if(ans)printf("%d\n",ans);
else puts("0");
}
return 0;
}

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