Question

How to rearrange an array such that every odd index element is greater than its previous in C

Answer 1

#include <stdio.h>

void swap(int arr[], int i, int j) {
    int temp = arr[i];
    arr[i] = arr[j];
    arr[j] = temp;
}
  
void rearrangeArray(int arr[], int size) {
    for (int i = 0; i < size - 1; i += 2) {
        if (arr[i] > arr[i + 1]) {
            swap(arr, i, i + 1);
        }
    }
    // if array size is odd
    if (size & 1) {
        for (int i = size - 1; i > 0; i -=2) {
            if (arr[i] > arr[i - 1]) {
                swap(arr, i, i - 1);
            }
        }
    }
}
  
int main(void)
{
    int arr[] = { 1, 3, 6, 5, 4, 2, 9, 8, 7 };
    int size = sizeof(arr) / sizeof(arr[0]);
  
    rearrangeArray(arr, size);
  
    for (int i = 0; i < size; i++) {
        printf("%d ", arr[i]);
    }
}
 
 
  
  
  
/*
run:
  
1 5 3 6 2 8 4 9 7
  
*/

 

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