C Exercises: Sort numbers using shell sorting method

C Programming Searching and Sorting Algorithm: Exercise-10 with Solution

Write a C program that sorts numbers using the shell sorting method.

According to Wikipedia "Shell sort or Shell's method, is an in-place comparison sort. It can be seen as either a generalization of sorting by exchange (bubble sort) or sorting by insertion (insertion sort). The method starts by sorting pairs of elements far apart from each other, then progressively reducing the gap between elements to be compared. Starting with far apart elements can move some out-of-place elements into position faster than a simple nearest neighbor exchange."

Sample Solution:

Sample C Code:

// https://bit.ly/2rcvXK5
// Shell Sort Implementation
// Source: https://bit.ly/2rcvXK5
#include <stdio.h>
// Function to perform shell sort on an array
void shell_sort(int *a, int n) {
    int h, i, j, t;
    // Iterate over different values of h (gap sequence)
    for (h = n; h /= 2;) {
        // Iterate through the array with the current gap h
        for (i = h; i < n; i++) {
            t = a[i];
            // Insertion sort within the subarrays created by the gap
            for (j = i; j >= h && t < a[j - h]; j -= h) {
                a[j] = a[j - h];
            }
            // Place the current element in its correct position
            a[j] = t;
        }
    }
}
// Main function
int main(int ac, char **av) {
    // Input array
    int a[] = {4, 65, 2, -31, 0, 99, 2, 83, 782, 1};
    int n = sizeof a / sizeof a[0];
    int i;
    // Display original array
    printf("Original Array:\n");
    for (i = 0; i < n; i++)
        printf("%d%s", a[i], i == n - 1 ? "\n" : " ");
    // Sort the array using shell sort
    shell_sort(a, n);
    // Display sorted array
    printf("\nSorted Array:\n");
    for (i = 0; i < n; i++)
        printf("%d%s", a[i], i == n - 1 ? "\n" : " ");
    return 0;
}

Sample Output:

Original Array:
4 65 2 -31 0 99 2 83 782 1

Sorted Array:
-31 0 1 2 2 4 65 83 99 782

Flowchart:

C Programming Code Editor:

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