Recently in one interview, after some initial questions about sorting algorithms e.g. how do you write QuickSort or the difference between QuickSort and MergeSort, the interviewer asked about do you understand the difference between stable and unstable sorting algorithms? This question was new to my reader, so he says, Sorry, never heard about that. The story ended there, and Interviewer moved on to the next question but like many of us, my reader went on to find more unanswered questions and ultimately he asks me what is the meaning of a stable and unstable sorting algorithm? Some of you might be heard about it and many of you might not know about this distinction, I'll try to answer this question in this article.
