C program to separate even and odd numbers from an array in 3 ways

C program to separate even and odd numbers from an array and put them in different arrays:

In this example, we will learn how to separate odd and even numbers from an array and put it in different arrays with a C program. A number is called an even number if it is perfectly divisible by 2. Else, it is called an odd number. For example, 2, 4, 6, 8, etc. are Even numbers. I will show you different ways to write the C program in this post.

Method 1: By using a for loop:

With this method, we will use one for loop to filter out the array elements. The program will use the following steps:

1. Suppose, the number array is already provided to the program.
2. We need to create two more arrays to store the odd and even numbers.
3. The program will run one loop and check for each number if it is divisible by 2 or not.
4. If yes, it will append that value to the array of even numbers. Else, it will append it to the array of odd numbers.
5. At the end of the program, it will print out the odd and even number arrays.

C program to separate even and odd numbers of an array with a for loop:

The following program shows how to separate the even and odd numbers of an array with a for loop:

#include <stdio.h>

int main()
{
    // 1
    int i, j, k;

    // 2
    int num[10] = {1, 2, 3, 4, 5, 6, 7, 8, 9, 10};

    // 3
    int odd[10];
    int even[10];

    // 4
    j = 0;
    k = 0;

    for (i = 0; i < 10; i++)
    {
        // 5
        if (num[i] % 2 == 0)
        {
            even[j] = num[i];
            j++;
        }
        else
        {
            odd[k] = num[i];
            k++;
        }
    }

    // 6
    printf("Even numbers: ");
    for (i = 0; i < j; i++)
    {
        printf("%d ", even[i]);
    }

    printf("\nOdd numbers: ");
    for (i = 0; i < k; i++)
    {
        printf("%d ", even[i]);
    }

    printf("\n");
    return 0;
}

Download the program on GitHub

Explanation:

The commented numbers in the above program denote the steps below :

1. Declare three integer variables i, j, and k.
2. The array num is the given array of integers. In this example, the size of this array is 10.
3. Initialize two integer arrays odd and even to hold the odd and even numbers of the array num.
4. Initialize j and k as 0. The integer variable j is used as the current index of the array odd and the variable k is used as the current index of the array even. It uses one for loop to iterate over the values of the num array.
5. For each element of num, it checks if it is even or odd. If it is even, it adds that value to the even array. Else, it adds it to the odd array. It also increments the value of j or k to point to the next position of the array.
6. At the end of the program, it prints the elements of the even and odd arrays.

Output :

Even numbers: 2 4 6 8 10
Odd numbers: 1 3 5 7 9

Method 2: C program to separate even and odd numbers with user input values:

We can take the size of the array as input from the user before initializing the array. The following C program shows how to take the size of the array as input. This program will work for variable size arrays:

#include <stdio.h>

void printArray(int arr[], int length){
    for(int i = 0; i < length; i++){
        printf("%d ", arr[i]);
    }
}

int main()
{
    int i, j, k, size;

    printf("Enter the size of the array: ");
    scanf("%d", &size);

    int num[size];
    int odd[size];
    int even[size];

    for(i = 0; i < size; i++){
        printf("Enter the number for position %d: ", i);
        scanf("%d", &num[i]);
    }

    j = 0;
    k = 0;

    for (i = 0; i < size; i++)
    {
        if (num[i] % 2 == 0)
        {
            even[j] = num[i];
            j++;
        }
        else
        {
            odd[k] = num[i];
            k++;
        }
    }

    printf("Even numbers: ");
    printArray(even, j);

    printf("\nOdd numbers: ");
    printArray(odd, k);

    printf("\n");
    return 0;
}

Download the program on GitHub

• We created a new function printArray. This function takes one array and its length as the parameters and prints the content of the array. The main program calls this function to print the final array content.
• The size of the array is assigned to the size variable. It initializes the arrays with size length.

If you run this program, it will print similar output.

Method 3: By using a while loop:

The following program shows how to use while loops to write the above program. The variable used in the loop is initialized before the loop starts and its value is incremented at the end of each iteration of the loop:

#include <stdio.h>

void printArray(int arr[], int length)
{
    int i = 0;
    while (i < length)
    {
        printf("%d ", arr[i]);
        i++;
    }
}

int main()
{
    int i, j, k, size;

    printf("Enter the size of the array: ");
    scanf("%d", &size);

    int num[size];
    int odd[size];
    int even[size];

    i = 0;
    while (i < size)
    {
        printf("Enter the number for position %d: ", i);
        scanf("%d", &num[i]);
        i++;
    }

    i = 0, j = 0, k = 0;

    while (i < size)
    {
        if (num[i] % 2 == 0)
        {
            even[j] = num[i];
            j++;
        }
        else
        {
            odd[k] = num[i];
            k++;
        }
        i++;
    }

    printf("Even numbers: ");
    printArray(even, j);

    printf("\nOdd numbers: ");
    printArray(odd, k);

    printf("\n");
    return 0;
}

Download the program on GitHub

The only difference in this program is that the for loops are replaced with while loops. The other parts of the program are not changed. It will print similar output.

You might also like:

• C program to convert a decimal number to octal
• C program to swap two numbers using call by reference
• C program to check if a substring exists in a string or not
• C program to check if a number is a perfect number or not
• C program compare two numbers without using if-else
• C program to convert seconds into hour/minute/seconds