算法学习之排序(一)(java)

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好记性不如烂笔头，仅以记之

排序接口

/** * 排序接口 * @author kongge * */public interface ISort {    public void sort(int[] numbers);}

/** * 数据接口 * @author kongge * */public interface ISortConstants {    public static final int TYPE_SORT_BUBBLE                             = 1;            // 冒泡排序    public static final int TYPE_SORT_BUCKET                             = 2;            // 桶排序    public static final int TYPE_SORT_QUICK                                = 3;            // 快排}

/** * 排序简单工厂 * @author kongge * */public class SortFactory {    public static ISort createSort(int type) {        ISort sort = null;        switch (type) {        case ISortConstants.TYPE_SORT_BUBBLE:            sort = new BubbleSort();            break;        case ISortConstants.TYPE_SORT_BUCKET:            sort = new BucketSort();            break;        case ISortConstants.TYPE_SORT_QUICK:            sort = new QuickSort();            break;        default:            break;        }        return sort;    }}

一：桶排序

/** *  * @author kongge * @descrition 桶排序 * 桶排序是最快的排序算法，时间复杂度为O(1)，但是简单的桶排序只能排一定范围内的非负数 */public class BucketSort implements ISort {    public BucketSort() {    }    @Override    public void sort(int[] numbers) {        int size = numbers.length;        if (size <= 0) {            System.out.println("数量不能为空");            return;        }        // 找到最大的数        int maxNum = numbers[0];        for (int i = 0; i < numbers.length; i++) {            int num = numbers[i];            if (num < 0) {                System.out.println("只支持非负数的排序");                return;            }            maxNum = maxNum > num ? maxNum : num;        }        // 开辟maxNum + 1大的空间,        int[] sortArray = new int[maxNum + 1];        // 将对应的数装入下标为该数的桶        for (int i = 0; i < size; i++) {            int num = numbers[i];            sortArray[num] ++;        }        System.out.println("---after  sort-----");        int sortArraySize = sortArray.length;        for (int i = 0; i < sortArraySize; i++) {            for (int j = 1; j <= sortArray[i]; j++) {                System.out.print(" " + i);            }        }        System.out.println("\n---end------");    }}

二：冒泡排序

/** *  * @author kongge *  @description 冒泡排序 *  时间复杂度O(n^2) *  将第一个数依次跟后面的数比较，如果比后面的大，则交换，一直比到size - i - 1（优化，不必每次比到最后） */public class BubbleSort implements ISort{    public BubbleSort() {    }    @Override    public void sort(int[] numbers) {        if (numbers.length <= 1) {            return;        }        System.out.println("---start sort----------");        int size = numbers.length;        for (int i = 0; i < size; i++) {            for (int j = 0; j < (size - i - 1); j++) {                int first = numbers[j];                int second = numbers[j + 1];                int temp = 0;                if (first > second) {                    temp = numbers[j];                    numbers[j] = numbers[j + 1];                    numbers[j + 1] = temp;                }            }        }        for (int i = 0; i < size; i++) {            System.out.print(" " + numbers[i]);        }        System.out.println("\n---end sort----------");    }

三：快速排序

/** * 快排 *  * @author kongge * 时间复杂度O(nlogn) *  */public class QuickSort implements ISort {    public QuickSort() {    }    @Override    public void sort(int[] numbers) {        if (numbers == null || numbers.length <= 1) {            return;        }        System.out.println("快速排序:");        sortLeftAndRight(numbers, 0, numbers.length - 1);    }    private void sortLeftAndRight(int[] numbers, int left, int right) {        if (left >= right) {            return;        }        int standeredNum = numbers[left];        int leftPoint = left;        int rightPoint = right;        while (leftPoint < rightPoint) {            while (leftPoint < rightPoint && numbers[rightPoint] >= standeredNum) {                rightPoint--;            }            while (leftPoint < rightPoint && numbers[leftPoint] <= standeredNum) {                leftPoint++;            }            if (leftPoint != rightPoint) {                int temp = numbers[leftPoint];                numbers[leftPoint] = numbers[rightPoint];                numbers[rightPoint] = temp;            }        }        int temp = numbers[leftPoint];        numbers[leftPoint] = numbers[left];        numbers[left] = temp;        sortLeftAndRight(numbers, left, leftPoint - 1);        sortLeftAndRight(numbers, leftPoint + 1, right);    }}

使用：

public class Client {    public static void main(String[] args) {        int[] array = {0, 2, 8, 77, 3, 9, 8, 3, 1, 3, 4, 3};        sortAndPrint(array, ISortConstants.TYPE_SORT_QUICK);    }    private static void sortAndPrint(int[] numbers, int sortType) {        ISort sort = SortFactory.createSort(sortType);        if (sort == null) {            System.out.println("请指定一种排序方式");            return;        }        System.out.println("---start  sort-----");        sort.sort(numbers);        int size = numbers.length;        for (int i = 0; i < size; i++) {            System.out.print(" " + numbers[i]);        }        System.out.println("\n---end  sort-----");    }}

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