PHP Interview finishing (b) data structure basis - the usual sort

2019-09-0119:04:39

PHP graduating students, on the Internet read a lot of interviews and information related stuff, here recorded, some places may be related to the original others, but at that time did not have time to add notes, if offended, please tell me, I will add the source is acknowledged. (Learning on the way there are a lot of mistakes, and ignoring the place, I hope you will correct me, thank you !!!)

Data structure here is really super important, regret sophomore did not take time to learn, did not take note of it, many of which are know these, I do not know why, so write this, intended as a study notes (the first to write ordering and tree) welcome to correct and supplement.

Common sorting algorithm

Source: Figure

First, the bubble sort (taken from Wikipedia)

It is a simple sorting algorithm, which repeatedly visited the number of columns to be sorted, a comparison of two elements, if they put them in the wrong order switching over. The number of visits to the column work is carried out repeatedly, there is no need to exchange know, that the number of columns already sorted completed. The origin of the name of the algorithm is because the smaller elements via exchange, slowly "float" to the top of the columns.

My understanding is relatively adjacent, then swap.

(Sophomore textbook)

(Screenshot from Wikipedia)

In the best case, the time complexity is O (n)

In the worst case, the time complexity is O (n- ² )

On the average, the same is O (n- ² )

It is a stable sorting algorithm

Second, the quick sort

Quick sort using a divide and conquer strategy to put a sequence into smaller and larger of the two sequences, then recursively sort of two sub-sequences

I understand: from the beginning to the middle to find the two, if the exchange position occurs, change direction until i, j equal.