Question

write a program to input a number N and print the nearest prime number smaller than the number​

Answer 1

Explanation:

/ Java program to print the

// nearest prime number by

// sequentially adding the

// prime numbers

import java.util.*;

class GFG

{

// Function to store prime

// numbers using prime seive

static void prime_seive(int MAX, int []isprime,

Vector<Integer> prime)

{

// iterate for all

// the numbers

int i = 2;

while (i * i <= MAX)

{

// If prime[p] is not changed,

// then it is a prime

if (isprime[i] == 1)

{

// append the prime

// to the list

prime.add(i);

// Update all multiples of p

for (int j = i * 2;

j < MAX; j += i)

{

isprime[j] = 0;

}

}

i += 1;

}

}

// Function to print

// the nearest prime

static int printNearest(int N)

{

int MAX = (int) 1e6;

// store all the

// index with 1 except 0,1 index

int [] isprime = new int[MAX];

for(int i = 2; i < MAX; i++)

isprime[i] = 1;

// list to store

// prime numbers

Vector<Integer> prime = new Vector<Integer>();

// variable to add primes

int i = 0;

// call the seive function

prime_seive(MAX, isprime, prime);

// Keep on adding prime

// numbers till the nearest

// prime number is achieved

while (isprime[N] == 0)

{

N += prime.get(i);

i += 1;

}

// return the

// nearest prime

return N ;

}

// Driver Code

public static void main(String[] args)

{

int N = 8;

System.out.printf("%d", printNearest(N));

}

}

hope it will help for you......