Quick Sort and Binary Tree Preorder
Prerequisite Knowledge
Before reading this article, you should first learn:
Summary in One Sentence
The core idea of quicksort can be understood by combining it with Preorder Traversal of Binary Trees: Position an element correctly in the preorder position during tree traversal, then recursively position the remaining elements.
Does this one-sentence summary leave beginners puzzled? How does array sorting relate to binary trees?
This illustrates that computer logic differs from human logic.
When a typical person sorts an array, they usually maintain a sortedIndex, ensuring [0, sortedIndex) is sorted, gradually moving sortedIndex to the right until the entire array is sorted. This process involves overcoming various challenges, as discussed in Selection Sort, Bubble Sort, Insertion Sort, and Shell Sort.
However, the more efficient an algorithm is, the closer it aligns with computer logic, making it harder for the untrained to understand. Having studied the earlier basic sorting algorithms, you should now realize this: sorting algorithms that are easy to understand and derive have complexities of . Breaking through the barrier involves algorithms that seem beyond human conception.
If someone casually says, "Sorting an array is easy; just sort one element, then sort the remaining elements, and the whole array will be sorted," you might think they are a Trisolaran agent secretly residing on Earth. 😃