BZOJ 1878 HH的项链(主席树)

# include <cstdio>
# include <cstring>
# include <cstdlib>
# include <iostream>
# include <vector>
# include <queue>
# include <stack>
# include <map>
# include <set>
# include <cmath>
# include <algorithm>
using namespace std;
# define lowbit(x) ((x)&(-x))
# define pi 3.1415926535
# define eps 1e-9
# define MOD 1000000009
# define INF 1000000000
# define mem(a,b) memset(a,b,sizeof(a))
# define FOR(i,a,n) for(int i=a; i<=n; ++i)
# define FO(i,a,n) for(int i=a; i<n; ++i)
# define bug puts("H");
# define lch p<<1,l,mid
# define rch p<<1|1,mid+1,r
# define mp make_pair
# define pb push_back
typedef pair<int,int> PII;
typedef vector<int> VI;
# pragma comment(linker, "/STACK:1024000000,1024000000")
typedef long long LL;
int Scan() {
    int res=0, flag=0;
    char ch;
    if((ch=getchar())==‘-‘) flag=1;
    else if(ch>=‘0‘&&ch<=‘9‘) res=ch-‘0‘;
    while((ch=getchar())>=‘0‘&&ch<=‘9‘)  res=res*10+(ch-‘0‘);
    return flag?-res:res;
}
void Out(int a) {
    if(a<0) {putchar(‘-‘); a=-a;}
    if(a>=10) Out(a/10);
    putchar(a%10+‘0‘);
}
const int N=50005;
//Code begin...

int root[N], s[N*80], ls[N*80], rs[N*80], sz, vis[1000005], to[N];

void insert(int l, int r, int x, int &y, int val){
    y=++sz;
    s[y]=s[x]+1;
    if (l==r) return ;
    ls[y]=ls[x]; rs[y]=rs[x];
    int mid=(l+r)>>1;
    if (val<=mid) insert(l,mid,ls[x],ls[y],val);
    else insert(mid+1,r,rs[x],rs[y],val);
}
int query(int l, int r, int x, int y, int L){
    if (r<L) return 0;
    if (l>=L) return s[y]-s[x];
    int mid=(l+r)>>1;
    return query(l,mid,ls[x],ls[y],L)+query(mid+1,r,rs[x],rs[y],L);
}
int main()
{
    int n, m, l, r, x;
    scanf("%d",&n);
    FOR(i,1,n) {
        scanf("%d",&x);
        if (vis[x]) to[vis[x]]=i;
        vis[x]=i;
    }
    FOR(i,1,n) if (to[i]==0) to[i]=n+1;
    FOR(i,1,n) insert(1,n+1,root[i-1],root[i],to[i]);
    scanf("%d",&m);
    FOR(i,1,m) {
        scanf("%d%d",&l,&r);
        printf("%d\n",query(1,n+1,root[l-1],root[r],r+1));
    }
    return 0;
}