给定一个包含非负整数的数组arr ,任务是打印数组中最长的素数子序列的长度。
例子:
Input: arr[] = { 3, 4, 11, 2, 9, 21 }
Output: 3
Longest Prime Subsequence is {3, 2, 11} and hence the answer is 3.
Input: arr[] = { 6, 4, 10, 13, 9, 25 }
Output: 1
方法:
- 遍历给定数组。
- 对于数组中的每个元素,检查它是否为素数。
- 如果元素是素数,它将在最长素数子序列中。因此,将最长素数子序列的所需长度增加 1
下面是上述方法的实现:
C++
// C++ program to find the length of
// Longest Prime Subsequence in an Array
#include
using namespace std;
#define N 100005
// Function to create Sieve
// to check primes
void SieveOfEratosthenes(
bool prime[], int p_size)
{
// False here indicates
// that it is not prime
prime[0] = false;
prime[1] = false;
for (int p = 2; p * p <= p_size; p++) {
// If prime[p] is not changed,
// then it is a prime
if (prime[p]) {
// Update all multiples of p,
// set them to non-prime
for (int i = p * 2;
i <= p_size;
i += p)
prime[i] = false;
}
}
}
// Function to find the longest subsequence
// which contain all prime numbers
int longestPrimeSubsequence(int arr[], int n)
{
bool prime[N + 1];
memset(prime, true, sizeof(prime));
// Precompute N primes
SieveOfEratosthenes(prime, N);
int answer = 0;
// Find the length of
// longest prime subsequence
for (int i = 0; i < n; i++) {
if (prime[arr[i]]) {
answer++;
}
}
return answer;
}
// Driver code
int main()
{
int arr[] = { 3, 4, 11, 2, 9, 21 };
int n = sizeof(arr) / sizeof(arr[0]);
// Function call
cout << longestPrimeSubsequence(arr, n)
<< endl;
return 0;
}
Java
// Java program to find the length of
// Longest Prime Subsequence in an Array
import java.util.*;
class GFG
{
static final int N = 100005;
// Function to create Sieve
// to check primes
static void SieveOfEratosthenes(
boolean prime[], int p_size)
{
// False here indicates
// that it is not prime
prime[0] = false;
prime[1] = false;
for (int p = 2; p * p <= p_size; p++) {
// If prime[p] is not changed,
// then it is a prime
if (prime[p]) {
// Update all multiples of p,
// set them to non-prime
for (int i = p * 2;
i <= p_size;
i += p)
prime[i] = false;
}
}
}
// Function to find the longest subsequence
// which contain all prime numbers
static int longestPrimeSubsequence(int arr[], int n)
{
boolean []prime = new boolean[N + 1];
Arrays.fill(prime, true);
// Precompute N primes
SieveOfEratosthenes(prime, N);
int answer = 0;
// Find the length of
// longest prime subsequence
for (int i = 0; i < n; i++) {
if (prime[arr[i]]) {
answer++;
}
}
return answer;
}
// Driver code
public static void main(String[] args)
{
int arr[] = { 3, 4, 11, 2, 9, 21 };
int n = arr.length;
// Function call
System.out.print(longestPrimeSubsequence(arr, n)
+"\n");
}
}
// This code is contributed by 29AjayKumar
Python3
# Python 3 program to find the length of
# Longest Prime Subsequence in an Array
N = 100005
# Function to create Sieve
# to check primes
def SieveOfEratosthenes(prime, p_size):
# False here indicates
# that it is not prime
prime[0] = False
prime[1] = False
p = 2
while p * p <= p_size:
# If prime[p] is not changed,
# then it is a prime
if (prime[p]):
# Update all multiples of p,
# set them to non-prime
for i in range( p * 2, p_size + 1, p):
prime[i] = False
p += 1
# Function to find the longest subsequence
# which contain all prime numbers
def longestPrimeSubsequence( arr, n):
prime = [True]*(N + 1)
# Precompute N primes
SieveOfEratosthenes(prime, N)
answer = 0
# Find the length of
# longest prime subsequence
for i in range (n):
if (prime[arr[i]]):
answer += 1
return answer
# Driver code
if __name__ == "__main__":
arr = [ 3, 4, 11, 2, 9, 21 ]
n = len(arr)
# Function call
print (longestPrimeSubsequence(arr, n))
# This code is contributed by chitranayal
C#
// C# program to find the length of
// longest Prime Subsequence in an Array
using System;
class GFG
{
static readonly int N = 100005;
// Function to create Sieve
// to check primes
static void SieveOfEratosthenes(
bool []prime, int p_size)
{
// False here indicates
// that it is not prime
prime[0] = false;
prime[1] = false;
for (int p = 2; p * p <= p_size; p++) {
// If prime[p] is not changed,
// then it is a prime
if (prime[p]) {
// Update all multiples of p,
// set them to non-prime
for (int i = p * 2;
i <= p_size;
i += p)
prime[i] = false;
}
}
}
// Function to find the longest subsequence
// which contain all prime numbers
static int longestPrimeSubsequence(int []arr, int n)
{
bool []prime = new bool[N + 1];
for (int i = 0; i < N+1; i++)
prime[i] = true;
// Precompute N primes
SieveOfEratosthenes(prime, N);
int answer = 0;
// Find the length of
// longest prime subsequence
for (int i = 0; i < n; i++) {
if (prime[arr[i]]) {
answer++;
}
}
return answer;
}
// Driver code
public static void Main(String[] args)
{
int []arr = { 3, 4, 11, 2, 9, 21 };
int n = arr.Length;
// Function call
Console.Write(longestPrimeSubsequence(arr, n)
+"\n");
}
}
// This code is contributed by 29AjayKumar
Javascript
输出:
3
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