Description about the Program to express a number as a sum of two prime numbers
Get a number as input from the user and express that number as sum of two prime numbers.
Input
4
Output
4 can be expressed as sum of 2 and 2
C Program to express a number as a sum of two prime numbers
#include <stdio.h>
int sumprimes(int n)
{
int i, isPrime = 1;
for(i = 2; i <= n/2; ++i)
{
if(n % i == 0)
{
isPrime = 0;
break;
}
}
return isPrime;
}
int main()
{
int num, i;
printf("Insert the num: ");
scanf("%d", &num);
int flag = 0;
for(i = 2; i <= num/2; ++i)
{
if(sumprimes(i) == 1)
{
if(sumprimes(num-i) == 1)
{
printf("%d can be expressed as the sum of %d and %d", num, i,num-i);
flag = 1;
}
}
}
if(flag == 0)
printf("%d cannot be expressed as the sum of two primes", num);
return 0;
}
C++ Program to express a number as a sum of two prime numbers
#include <iostream>
using namespace std;
int sumprimes(int n)
{
int i, isPrime = 1;
for(i = 2; i <= n/2; ++i)
{
if(n % i == 0)
{
isPrime = 0;
break;
}
}
return isPrime;
}
int main()
{
int num, i;
cout<<"Insert the num: ";
cin>>num;
int flag = 0;
for(i = 2; i <= num/2; ++i)
{
if(sumprimes(i) == 1)
{
if(sumprimes(num-i) == 1)
{
cout<<num<<" can be expressed as the sum of "<<i<<" and "<<num-i;
flag = 1;
}
}
}
if(flag == 0)
cout<<num<<" cannot be expressed as the sum of two primes";
return 0;
}
Java Program to express a number as a sum of two prime numbers
import java.util.Scanner;
public class Main
{
static int sumprimes(int n)
{
int i, isPrime = 1;
for(i = 2; i <= n/2; ++i)
{
if(n % i == 0)
{
isPrime = 0;
break;
}
}
return isPrime;
}
public static void main(String[] args) {
Scanner sc = new Scanner(System.in);
System.out.print("Enter a number : ");
int num = sc.nextInt();
int flag = 0;
for(int i = 2; i <= num/2; ++i)
{
if(sumprimes(i) == 1)
{
if(sumprimes(num-i) == 1)
{
System.out.println(num+" can be expressed as the sum of "+i+" and "+(num-i));
flag = 1;
}
}
}
if(flag == 0)
System.out.println(num+" cannot be expressed as the sum of two primes");
}
}
Python Program to express a number as a sum of two prime numbers
num = int(input('Enter a number :'))
arr = []
for i in range(2,num):
flag = 0
for j in range(2,i):
if i % j == 0:
flag = 1
if flag == 0:
arr.append(i)
flag = 0
for i in range(len(arr)):
for j in range(i+1,len(arr)):
if(arr[i] + arr[j] == num):
flag = 1
print(str(num) + " can be expressed as the sum of " + str(arr[i]) + " and " + str(arr[j]))
break
if(flag == 0):
print('No Prime numbers can give sum of ' + str(num))
