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在线主席树查询区间多少个不同的数.cpp
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在线主席树查询区间多少个不同的数.cpp
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#include<bits/stdc++.h>
using namespace std;
const int maxn=1e6+50;
int n,m;
int a[maxn];
int last[maxn];
int num;
int rt[maxn];
struct Seg
{
int l,r;
int ls,rs;
int sum;
int mid(){return l+((r-l)>>1);}
}seg[maxn*40];
int build(int l,int r)
{
int pos=num++;
seg[pos].l=l;
seg[pos].r=r;
seg[pos].sum=0;
if(l == r)
return pos;
int mid=(l+r)>>1;
seg[pos].ls=build(l,mid);
seg[pos].rs=build(mid+1,r);
return pos;
}
int clone(int pos)
{
seg[num]=seg[pos];
return num++;
}
void pushUp(int pos)
{
seg[pos].sum=seg[seg[pos].ls].sum+seg[seg[pos].rs].sum;
}
int update(int pos,int x,int val)
{
pos=clone(pos);
if(seg[pos].l == seg[pos].r)
{
seg[pos].sum += val;
return pos;
}
int mid=seg[pos].mid();
if(x <= mid)
seg[pos].ls=update(seg[pos].ls,x,val);
else
seg[pos].rs=update(seg[pos].rs,x,val);
pushUp(pos);
return pos;
}
int query(int pos,int l,int r)
{
if(seg[pos].l == l && seg[pos].r == r)
return seg[pos].sum;
int mid=seg[pos].mid();
if(r <= mid)
return query(seg[pos].ls,l,r);
else if(l > mid)
return query(seg[pos].rs,l,r);
else
return query(seg[pos].ls,l,mid)+query(seg[pos].rs,mid+1,r);
}
void Solve()
{
num=0;
rt[0]=build(1,n);
for(int i=1;i <= n;++i)
{
int tmp=rt[i-1];
if(last[a[i]])
tmp=update(rt[i-1],last[a[i]],-1);
rt[i]=update(tmp,i,1);
last[a[i]]=i;
}
scanf("%d",&m);
while(m--)
{
int l,r;
scanf("%d%d",&l,&r);
printf("%d\n",query(rt[r],l,r));
}
}
int main()
{
scanf("%d",&n);
for(int i=1;i <= n;++i)
{
scanf("%d",a+i);
last[a[i]]=0;
}
Solve();
return 0;
}