C Exercises: Segregate even and odd elements on an array

Last update on March 18 2025 13:20:55 (UTC/GMT +8 hours)

96. Segregate Even and Odd Elements

Write a program in C to segregate even and odd elements in an array.

Expected Output:
The given array is:
17 42 19 7 27 24 30 54 73
The array after segregation is: 54 42 30 24 27 7 19 17 73

The task is to write a C program that segregates even and odd elements in a given array, such that all even elements are moved to the beginning and all odd elements to the end of the array. The program should iterate through the array, rearrange the elements accordingly, and then display the modified array with all even numbers followed by all odd numbers.

Sample Solution:

C Code:

#include<stdio.h>

// Function to swap two elements
void changePlace(int *ar, int *br) 
{ 
    int temp = *ar; 
    *ar = *br; 
    *br = temp; 
} 

// Function to segregate even and odd numbers in an array
void EvenOddSegre(int arr1[], int size) 
{ 
    int l_index = 0, r_index = size - 1; 

    // Segregating even and odd numbers
    while (l_index < r_index) 
    { 
        // Move left_index until an odd number is found
        while (arr1[l_index] % 2 == 0 && l_index < r_index) 
            l_index++; 

        // Move right_index until an even number is found
        while (arr1[r_index] % 2 == 1 && l_index < r_index) 
            r_index--; 

        // Swap the found odd and even elements
        if (l_index < r_index) 
        { 
            changePlace(&arr1[l_index], &arr1[r_index]); 
            l_index++; 
            r_index--; 
        } 
    } 
} 

int main() 
{ 
    int arr1[] = {17, 42, 19, 7, 27, 24, 30, 54, 73}; 
    int arr_size = sizeof(arr1) / sizeof(arr1[0]); 
    int i = 0; 

    // Print the original array
    printf("The given array is:  \n");
    for(i = 0; i < arr_size; i++)
    {
        printf("%d  ", arr1[i]);
    }
    printf("\n");

    // Segregate even and odd numbers
    EvenOddSegre(arr1, arr_size); 

    // Print the segregated array
    printf("The array after segregation is:  "); 
    for (i = 0; i < arr_size; i++) 
        printf("%d ", arr1[i]); 

    return 0; 
}  

Output:

The given array is:  
17  42  19  7  27  24  30  54  73  
The array after segregation is:  54 42 30 24 27 7 19 17 73

Visual Presentation:

Flowchart:/p>

For more Practice: Solve these Related Problems:

• Write a C program to segregate even and odd numbers in an array using a two-pointer approach.
• Write a C program to segregate evens and odds and then sort each partition separately.
• Write a C program to rearrange an array such that all evens come before odds using pointer arithmetic.
• Write a C program to segregate even and odd elements and then merge them in alternating order.

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