1878: [SDOI2009]HH的项 莫队算法-离线查询区间内部不同数字的个数

#include<iostream>
#include<stdio.h>
#include<string.h>
#include<algorithm>
#include<math.h>
using namespace std;
const int maxx = 1e6+6;
int a[maxx];
int vis[maxx];
int ans[maxx];
int block;
int res;
struct node
{
    int l,r;
    int id;
    friend bool operator < (node &a,node &b)
    {
        if (a.l/block==b.l/block)
        {
            return a.r<b.r;
        }
        return a.l/block<b.l/block;
    }
} que[maxx];
void add(int x)
{
    vis[a[x]]++;
    if (vis[a[x]]==1)
        res++;
}
void del(int x)
{
    vis[a[x]]--;
    if (vis[a[x]]==0)
    {
        res--;
    }
}
int main()
{
    int n,q;
    while(~scanf("%d",&n))
    {
        res=0;
        block=sqrt(n);
        memset(vis,0,sizeof(vis));
        for (int i=1; i<=n; i++)
        {
            scanf("%d",&a[i]);
        }
        scanf("%d",&q);
        int l=1,r=0;
        for (int i=1; i<=q; i++)
        {
            scanf("%d%d",&que[i].l,&que[i].r);
            que[i].id=i;
        }
        sort(que+1,que+1+q);
        for (int i=1; i<=q; i++)
        {
            while(l<que[i].l)del(l),l++;
            while(l>que[i].l)l--,add(l);
            while(r<que[i].r)r++,add(r);
            while(r>que[i].r)del(r),r--;
            ans[que[i].id]=res;
        }
        for (int i=1;i<=q;i++){
            if (i-1)printf(" %d",ans[i]);
            else printf("%d",ans[i]);
        }
    }
    return 0;
}