How does the strand sort algorithm work?

The Strand Sort algorithm works by repeatedly pulling sorted sublists out of the unsorted list and merging them together.

Strand Sort is a comparison-based sorting algorithm. It operates by dividing the original unsorted list into smaller sorted sublists, and then repeatedly merging these sublists together until the entire list is sorted. The name 'Strand Sort' comes from the way the algorithm 'strands' or isolates sorted sequences from the unsorted list.

The algorithm begins by examining the first element in the list. This element forms the beginning of a new sublist. The algorithm then continues through the rest of the list, checking each element in turn. If an element is found that is larger than the last element in the current sublist, it is removed from the main list and added to the end of the sublist. This process continues until the end of the list is reached, at which point the sublist is fully sorted and is merged back into the main list.

The merging process is also straightforward. The algorithm compares the first elements of the main list and the sublist. The smaller element is removed from its list and added to the end of the output list. This process continues until one of the lists is empty, at which point all remaining elements from the non-empty list are added to the end of the output list.

The algorithm then repeats this process, creating a new sublist from the remaining unsorted elements in the main list, and merging it into the output list, until the main list is empty and all elements have been sorted.

Strand Sort is an efficient algorithm for sorting lists where many elements are already in order. However, its worst-case time complexity is O(n^2), which makes it less suitable for large lists or lists that are very out of order. Despite this, it's a great algorithm to understand as it helps to reinforce the concept of divide and conquer, a fundamental principle in computer science.