C++ program to Check Number can Express as Sum of Prime Numbers

What are Functions ?

Function is a block of statements that performs some operations. All C++ programs have at least one function – function called “main()”. This function is entry-point of your program.

A function declaration tells the compiler about a function’s name, return type, and parameters. A function definition provides the actual body of the function.

Defining a Function : :

The general form of a C++ function definition is as follows

return_type Function_Name( list of parameters )
{
//function’s body
}

• return_type : suggests what the function will return. It can be void, int, char, some pointer or even a class object.
• Function_Name : is the name of the function, using the function name it is called.
• Parameters : are variables to hold values of arguments passed while function is called. A function may or may not contain parameter list.
• Function body : is he part where the code statements are written.

Below is the source code for C++ program to Check Number can Express as Sum of Prime Numbers which is successfully compiled and run on Windows System to produce desired output as shown below :

SOURCE CODE : :

/* C++ program to Check Number can Express as Sum of Prime Numbers  */

#include <iostream>
using namespace std;

bool checkPrime(int n);

int main()
{
    int n, i;
    bool flag = false;

    cout << "\nEnter any positive  integer :: ";
    cin >> n;
    cout<<"\n";

    for(i = 2; i <= n/2; ++i)
    {
        if (checkPrime(i))
        {
            if (checkPrime(n - i))
            {
                cout << n << " = " << i << " + " << n-i << endl;
                flag = true;
            }
        }
    }

    if (!flag)
      cout <<"\nThe Number [ "<< n << " ] can't be expressed as sum of two prime numbers.\n";

    return 0;
}

// Check prime number
bool checkPrime(int n)
{
    int i;
    bool isPrime = true;

    for(i = 2; i <= n/2; ++i)
    {
        if(n % i == 0)
        {
            isPrime = false;
            break;
        }
    }

    return isPrime;
}

OUTPUT : :

/* C++ program to Check Number can Express as Sum of Prime Numbers  */

Enter any positive  integer :: 1234

1234 = 3 + 1231
1234 = 5 + 1229
1234 = 11 + 1223
1234 = 17 + 1217
1234 = 41 + 1193
1234 = 47 + 1187
1234 = 53 + 1181
1234 = 71 + 1163
1234 = 83 + 1151
1234 = 131 + 1103
1234 = 137 + 1097
1234 = 173 + 1061
1234 = 251 + 983
1234 = 257 + 977
1234 = 263 + 971
1234 = 281 + 953
1234 = 293 + 941
1234 = 347 + 887
1234 = 353 + 881
1234 = 461 + 773
1234 = 491 + 743
1234 = 557 + 677
1234 = 587 + 647
1234 = 593 + 641
1234 = 617 + 617

Process returned 0

Above is the source code for C++ program to Check Number can Express as Sum of Prime Numbers which is successfully compiled and run on Windows System.The Output of the program is shown above .