题目链接:https://vjudge.net/problem/SPOJ-DQUERY
解题思路:
莫队
代码:
#include<cstdio>
#include<cmath>
#include<cstring>
#include<algorithm>
#include<map>
#define ll long long
#define for0(i,a,b) for (int i = a; i < b; i++)
#define for1(i,a,b) for (int i = a; i <= b; i++)
using namespace std;
const int N = 3e4+5;
const int M = 2e5+5;
const int MAXV = 1e6+5;
int blo,bl[N],m,n;
int v[N];
int sum;
int cnt[MAXV];
int ans[M];
struct node
{
int l,r;
int id;
bool operator < (const node& a)const{
if (bl[l]==bl[a.l]) return r < a.r;
return bl[l] < bl[a.l];
}
}q[M];
void REMOVE(int x)
{
cnt[v[x]]--;
if (cnt[v[x]]==0) sum--;
}
void ADD(int x)
{
cnt[v[x]]++;
if (cnt[v[x]]==1) sum++;
}
void solve()
{
int nowl = 1,nowr = 0;
for1(i,1,m){
int tl = q[i].l,tr = q[i].r;
while (nowr<tr) ADD(++nowr);
while (nowl>tl) ADD(--nowl);
while (nowr>tr) REMOVE(nowr--);
while (nowl<tl) REMOVE(nowl++);
ans[q[i].id] = sum;
}
}
int main()
{
scanf("%d",&n);
blo = sqrt(n);
for1(i,1,n){
scanf("%d",v+i);
bl[i] = (i-1)/blo+1;
}
scanf("%d",&m);
for1(i,1,m){
scanf("%d %d",&q[i].l,&q[i].r);
q[i].id = i;
}
sort(q+1,q+1+m);
solve();
for1(i,1,m){
printf("%d\n",ans[i]);
}
return 0;
}