Sort of a common algorithm "bubble sort"

Bubble sort is a sort of algorithm that we basically get into contact with in the beginning of programming, since it is more concise and more image.

Its idea is to let each of the adjacent elements compare, if they do not follow the ascending or descending, then exchange their positions, repeat the operation, the largest or smallest elements like bubbles, rise to the top, the remaining elements repeat this operation, all the elements can be ordered.

The way it works:

1. Compare from the back, if the size between adjacent elements is not in ascending or descending order to compare them, if not specify the rules, then exchange their positions

2. According to (1), compare each pair in turn until the end

3. In addition to the above-selected maximum or minimum elements, repeat the above steps until there are no numbers to compare

so we can see that, without any optimization, the number of times it needs to be compared is O (n^2), which requires O (n) + O (1) space

Let's look at the code below:

    private static void Swap (int[] array, int from, int. to) {        int temp;        temp = Array[from];        Array[from] = array[to];        Array[to] = temp;    }    public static void sort (int[] array) {for        (int i = 0; i < array.length-1; i++) {for            (int j = 0; J < Array. Length-i-1; J + +) {                if (Array[j] > Array[j+1]) {                    swap (array, j+1, j);}        }}    

We have said that each time we need to compare adjacent elements, if one is not the last traversal, we find that there is no exchange, then it means that our array is already in order, so there is no need to continue the subsequent operation. So we can set a flag bit to check if we still need to compare.

    public static void sort (int[] array) {for        (int i = 0; i < array.length-1; i++) {            Boolean flag = true;            for (int j = 0; J < array.length-i-1; j + +) {                if (Array[j] > Array[j+1]) {                    swap (array, j + 1, j);                    Flag = false;                }            }            if (flag) {                return;}}    }

However, we seem to be able to find bubble sort also has a feature, bubble sort after the array, its top must be orderly, when we in a trip the last Exchange element position above is ordered, and is the largest or smallest of several elements. So in the next iteration, we don't have to compare them, and then combine the above flags, and we can change it to:

    public static void sort (int[] array) {        int exchange = ARRAY.LENGTH-1;           Location of the last interchange        while (Exchange > 0) {            int bound = Exchange;                   Last position of each Exchange            exchange  = 0;            for (int j = 0; J < bound; J + +) {                if (Array[j] > Array[j+1]) {                    swap (array, j + 1, j);                    Exchange = J;}}}    

Here, let's summarize:

Bubble sort, average time complexity O (n^2), Worst time complexity O (n^2), Optimal time complexity O (n), Worst space complexity O (n) + O (1)

Well, if you have a better way, welcome the message to discuss.

Sort the common algorithm one "bubble sort"