C++ Program for Comb Sort

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Comb Sort is mainly an improvement over Bubble Sort. Bubble sort always compares adjacent values. So all inversions are removed one by one. Comb Sort improves on Bubble Sort by using gap of size more than 1. The gap starts with a large value and shrinks by a factor of 1.3 in every iteration until it reaches the value 1. Thus Comb Sort removes more than one inversion counts with one swap and performs better than Bubble Sort.
The shrink factor has been empirically found to be 1.3 (by testing Combsort on over 200, 000 random lists) [Source: Wiki]Although, it works better than Bubble Sort on average, worst case remains O(n²).

CPP

// C++ implementation of Comb Sort
#include <bits/stdc++.h>
using namespace std;
 
// To find gap between elements
int getNextGap(int gap)
{
    // Shrink gap by Shrink factor
    gap = (gap * 10) / 13;
 
    if (gap < 1)
        return 1;
    return gap;
}
 
// Function to sort a[0..n-1] using Comb Sort
void combSort(int a[], int n)
{
    // Initialize gap
    int gap = n;
 
    // Initialize swapped as true to make sure that
    // loop runs
    bool swapped = true;
 
    // Keep running while gap is more than 1 and last
    // iteration caused a swap
    while (gap != 1 || swapped == true) {
        // Find next gap
        gap = getNextGap(gap);
 
        // Initialize swapped as false so that we can
        // check if swap happened or not
        swapped = false;
 
        // Compare all elements with current gap
        for (int i = 0; i < n - gap; i++) {
            if (a[i] > a[i + gap]) {
                swap(a[i], a[i + gap]);
                swapped = true;
            }
        }
    }
}
 
// Driver program
int main()
{
    int a[] = { 8, 4, 1, 56, 3, -44, 23, -6, 28, 0 };
    int n = sizeof(a) / sizeof(a[0]);
 
    combSort(a, n);
 
    printf("Sorted array: \n");
    for (int i = 0; i < n; i++)
        printf("%d ", a[i]);
 
    return 0;
}

Output:

Sorted array: 
-44 -6 0 1 3 4 8 23 28 56

Time Complexity: The worst-case complexity of this algorithm is O(n²).
Auxiliary Space: O(1).

Please refer complete article on Comb Sort for more details!

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