C++ で書かれており、部分配列内の素数の数を見つけます。

Input : arr[] = {1, 2, 3, 4, 5, 6}, q = 1, L = 0, R = 3

Output : 2

In the given range the primes are {2, 3}.

Input : arr[] = {2, 3, 5, 8 ,12, 11}, q = 1, L = 0, R = 5

Output : 4

In the given range the primes are {2, 3, 5, 11}.

#include <bits/stdc++.h>
using namespace std;
bool isPrime(int N){
    if (N <= 1)
       return false;
    if (N <= 3)
       return true;
    if(N % 2 == 0 || N % 3 == 0)
       return false;
    for (int i = 5; i * i <= N; i = i + 2){ // as even number can&#39;t be prime so we increment i by 2.
       if (N % i == 0)
           return false; // if N is divisible by any number then it is not prime.
    }
    return true;
}
int main(){
    int N = 6; // size of array.
    int arr[N] = {1, 2, 3, 4, 5, 6};
    int Q = 1;
    while(Q--){
        int L = 0, R = 3;
        int cnt = 0;
        for(int i = L; i <= R; i++){
           if(isPrime(arr[i]))
               cnt++; // counter variable.
        }
        cout << cnt << "\n";
    }
    return 0;
}

#include <bits/stdc++.h>
using namespace std;
vector<bool> sieveOfEratosthenes(int *arr, int n, int MAX){
    vector<bool> p(n);
    bool Prime[MAX + 1];
    for(int i = 2; i < MAX; i++)
       Prime[i] = true;
    Prime[1] = false;
    for (int p = 2; p * p <= MAX; p++) {
       // If prime[p] is not changed, then
       // it is a prime
       if (Prime[p] == true) {
           // Update all multiples of p
           for (int i = p * 2; i <= MAX; i += p)
               Prime[i] = false;
       }
    }
    for(int i = 0; i < n; i++){
        if(Prime[arr[i]])
           p[i] = true;
        else
           p[i] = false;
    }
    return p;
}
int main(){
    int n = 6;
    int arr[n] = {1, 2, 3, 4, 5, 6};
    int MAX = -1;
    for(int i = 0; i < n; i++){
        MAX = max(MAX, arr[i]);
    }
    vector<bool> isprime = sieveOfEratosthenes(arr, n, MAX); // boolean array.
    int q = 1;
    while(q--){
        int L = 0, R = 3;
        int cnt = 0; // count
        for(int i = L; i <= R; i++){
            if(isprime[i])
               cnt++;
       }
       cout << cnt << "\n";
   }
   return 0;
}