Example: Even-Odd Sort using Two Pointers in C

// Even-Odd Sort using Two Pointers
#include <stdio.h>

void swap(int *a, int *b) {
    int temp = *a;
    *a = *b;
    *b = temp;
}

void evenOddSortTwoPointers(int arr[], int n) {
    // Step 1: Initialize two pointers
    int left = 0;
    int right = n - 1;

    // Step 2: Iterate while left pointer is less than right pointer
    while (left < right) {
        // Step 3: Move left pointer while it points to an even number
        while (arr[left] % 2 == 0 && left < right) {
            left++;
        }

        // Step 4: Move right pointer while it points to an odd number
        while (arr[right] % 2 != 0 && left < right) {
            right--;
        }

        // Step 5: If left is still less than right, swap elements
        if (left < right) {
            swap(&arr[left], &arr[right]);
            left++;
            right--;
        }
    }
}

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

int main() {
    int arr[] = {12, 34, 45, 9, 8, 90, 3};
    int n = sizeof(arr) / sizeof(arr[0]);

    printf("Original array: ");
    printArray(arr, n);

    evenOddSortTwoPointers(arr, n);

    printf("Sorted array (Two Pointers): ");
    printArray(arr, n);

    int arr2[] = {7, 2, 10, 5, 1, 8, 4};
    n = sizeof(arr2) / sizeof(arr2[0]);

    printf("Original array: ");
    printArray(arr2, n);

    evenOddSortTwoPointers(arr2, n);

    printf("Sorted array (Two Pointers): ");
    printArray(arr2, n);

    return 0;
}