NKOJ P2387 [HZOI] 赏花【莫队板子】

这道题在没学莫队之前用树状数组和线段树写了好久…然而莫队直接秒杀树状数组线段树做法…

参考代码：

#include <cmath>
#include <cstdio>
#include <cstring>
#include <iostream>
#include <algorithm>
#define SG string
#define DB double
using namespace std;
const int Max1=2e5+5;
const int Max2=1e5+5;
struct Node{
    int X,Y,Id;
}Ask[Max1];
int N,M,S,Num,A[Max2],B[Max2],Cnt[Max2],Ans[Max1];
inline int Read(){
    int X=0;char CH=getchar();bool F=0;
    while(CH>'9'||CH<'0'){if(CH=='-')F=1;CH=getchar();}
    while(CH>='0'&&CH<='9'){X=(X<<1)+(X<<3)+CH-'0';CH=getchar();}
    return F?-X:X;
}
inline void Write(int X){
    if(X<0)X=-X,putchar('-');
    if(X>9)Write(X/10);
    putchar(X%10+48);
}
void Insert(int X){
    if(!Cnt[A[X]]){
        Num++;
    }Cnt[A[X]]++;
}
void Delete(int X){
    if(Cnt[A[X]]==1){
        Num--;
    }Cnt[A[X]]--;
}
bool Cmp(Node P,Node Q){
    return B[P.X]==B[Q.X]?P.Y<Q.Y:B[P.X]<B[Q.X];
}
int main(){
    int I,J,K;
    N=Read();S=sqrt(N);
    for(I=1;I<=N;I++){
        A[I]=Read();B[I]=I/S;
    }
    M=Read();
    for(I=1;I<=M;I++){
        Ask[I].Id=I;
        Ask[I].X=Read();
        Ask[I].Y=Read();
    }
    sort(Ask+1,Ask+1+M,Cmp);
    int Left=1,Right=1;Insert(1);
    for(I=1;I<=M;I++){
        while(Right<Ask[I].Y){
            Insert(++Right);
        }
        while(Right>Ask[I].Y){
            Delete(Right--);
        }
        while(Left<Ask[I].X){
            Delete(Left++);
        }
        while(Left>Ask[I].X){
            Insert(--Left);
        }
        Ans[Ask[I].Id]=Num;
    }
    for(I=1;I<=M;I++){
        Write(Ans[I]),putchar('\n');
    }
    return 0;
}