C Exercises: Create new array from a given array of integers shifting all even numbers before all odd numbers

Last update on March 18 2025 13:24:52 (UTC/GMT +8 hours)

73. Partition Array: Evens Before Odds

Write a C program to create an array from a given array of integers shifting all even numbers before all odd numbers.

C Code:

#include <stdio.h>
#include <stdlib.h>

// Function prototype for 'print_array'
void print_array(int parray[], int size);

int main(void){ 
    int arr_size;

    // Declaration and initialization of an integer array 'a1'
    int a1[] = {1, 2, 5, 3, 5, 4, 6, 9, 11};
    arr_size = sizeof(a1)/sizeof(a1[0]);

    // Printing the elements of the original array 'a1'
    printf("Elements in original array are: ");  
    print_array(a1, arr_size);

    // Declaration of 'size' and 'index' variables
    int size = arr_size, index = 0;

    // Loop to iterate through the elements of 'a1'
    for (int i = 0; i < size; i++)
    {
        // If the current element is even, swap it with the element at 'index'
        if (a1[i] % 2 == 0)
        {
            int temp = a1[index];
            a1[index] = a1[i];
            a1[i] = temp;

            index++;
        }
    }    

    // Printing the elements of the modified array 'a1'
    printf("\nElements in new array are: ");  
    print_array(a1, arr_size);
}         

// Definition of the 'print_array' function
void print_array(int parray[], int size)
{
    int i;      
    // Loop to print the elements of the array
    for( i = 0; i < size - 1; i++)  
    {  
        printf("%d, ", parray[i]);  
    } 
    // Printing the last element
    printf("%d ", parray[i]);  
    printf("\n");   
}

Sample Output:

Elements in original array are: 1, 2, 5, 3, 5, 4, 6, 9, 11 

Elements in new array are: 2, 4, 6, 3, 5, 1, 5, 9, 11

Pictorial Presentation:

Flowchart:

For more Practice: Solve these Related Problems:

• Write a C program to partition an array with odd numbers before even numbers.
• Write a C program to segregate an array into three parts: even, odd, and zeros in the middle.
• Write a C program to rearrange an array so that all multiples of 3 come before others.
• Write a C program to sort an array by parity: placing even numbers in ascending order followed by odd numbers in descending order.

C Programming Code Editor:

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