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添加排序算法，选择，插入，冒泡，快排
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‎src/main/java/cn/byhieg/algorithmtutorial/Sort.java‎

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package cn.byhieg.algorithmtutorial;
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/**
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* Created by shiqifeng on 2017/3/28.
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* Mail byhieg@gmail.com
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*/
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public class Sort {
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/**
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* 选择排序，每一轮排序，选择数组中数字最小的那一个放到指定的位置上。
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* 时间复杂度o(n^2),无论数组顺序如何都要选择一个最小的值，因为数组的是否有序，不影响时间复杂度
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* 空间复杂度o(1)
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* @param nums
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*/
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public void chooseSort(int[] nums) {
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int length = nums.length;
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for (int i = 0; i < length; i++) {
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int min = i;//申请额外的空间o(1)
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for (int j = i + 1; j < length; j++) {
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if (nums[min] > nums[j]) {
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min = j;
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}
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}
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//将最小的下标代表的数与i位置的进行交换
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int tmp = nums[i];
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nums[i] = nums[min];
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nums[min] = tmp;
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}
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}
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/**
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* 直接插入排序，每一轮排序，都是在i坐标之前，包括i坐标的序列是有序的，但是并不是最终的排序位置。
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* 时间复杂度o（n^2),对于第二重循环，只会在非有序的环境下才会执行每个元素后移，因此针对有序的数组，时间复杂度最好的情况是o(N)。
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* 空间复杂度o(1)
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* @param nums
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*/
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public void insertDirectlySort(int[] nums) {
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int length = nums.length;
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for (int i = 1; i < length; i++) {
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for (int j = i ; j > 0; j --) {
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if (nums[j] < nums[j - 1]) {
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int tmp = nums[j - 1];
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nums[j - 1] = nums[j];
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nums[j] = tmp;
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}
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}
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}
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}
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/**
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* 折半插入排序，针对直接排序而言，每一个要插入的元素都是插入在有序的数组中，因此，只需要查找到插入的位置即可，查找的方式利用二分查找
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* 时间复杂度和直接插入是一样的，只是快在了查找的过程中，还是o(N^2),最好的环境下是o（N）
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* 空间复杂度还是o(1)
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* @param nums
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*/
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public void insertBinarySort(int[] nums) {
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int length = nums.length;
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for (int i = 1; i < length;i++) {
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int tmp = nums[i];
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int low = 0;
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int high = i - 1;
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while (low <= high) {
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int mid = (low + high) / 2;
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if (tmp < nums[mid]) {
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high = mid - 1;
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}else{
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low = mid + 1;
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}
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}
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for (int j = i; j >= low + 1;j--) {
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nums[j] = nums[j - 1];
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}
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nums[low] = tmp;
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}
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}
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/**
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* 冒泡排序，每i轮排序，就是不断交换两个元素，直到将最大的元素放到n - i的位置上
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* 这种实现是按照算法定义的，但是效率是最低的
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* 时间复杂度o(n^2)
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* 空间复杂度o(1)
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* @param nums
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*/
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public void bubbleSort1(int[] nums) {
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int length = nums.length;
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for (int i = 1 ; i < length;i++) {
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for (int j = 0 ; j < length - i;j++) {
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if (nums[j] > nums[j + 1]) {
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int tmp = nums[j];
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nums[j] = nums[j + 1];
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nums[j+1] = tmp;
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}
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}
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}
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}
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/**
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* 冒泡排序，高效率实现，因为只需要用一个flag变量来记录本次的排序，是否修改
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* 如果没有修改，说明已经有序
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* @param nums
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*/
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public void bubbleSort2(int[] nums) {
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int length = nums.length;
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boolean flag = true;
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while (flag) {
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flag = false;
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for (int j = 0 ; j < length - 1;j++) {
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if (nums[j] > nums[j + 1]) {
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int tmp = nums[j];
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nums[j] = nums[j + 1];
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nums[j + 1] = tmp;
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flag = true;
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}
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}
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length -- ;
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}
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}
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/**
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* 快速排序，选定一个切分元素，每一轮排序后，都保证切分元素之前的元素都小于切分元素，切分元素之后的元素都大于切分元素
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*
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* @param nums
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*/
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public void quickSort(int[] nums) {
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int low = 0;
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int high = nums.length - 1;
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sort(nums, low, high);
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}
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/**
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* 快速排序的递归实现
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* @param nums
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* @param low
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* @param high
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*/
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public void sort(int[] nums, int low, int high) {
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if (low >= high) return;
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int j = partition(nums, low, high);
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sort(nums, low, j - 1);
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sort(nums, j + 1, high);
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}
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/**
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* 快速排序的辅助方法，来对排序的数组，进行切分,
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* @param nums
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* @param low
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* @param high
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* @return
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*/
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public int partition(int[] nums, int low, int high) {
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int i = low;
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int j = high;
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int x = nums[i];
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while (i < j) {
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//从右向左找到nums[j]小于x的元素
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while (i < j && nums[j] > x) j-- ;
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if (i < j) {
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nums[i] = nums[j];
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i++;
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}
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//从左向右找到nums[i]大于x的元素
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while (i < j && nums[i] < x) i++;
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if (i < j) {
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nums[j] = nums[i];
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j--;
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}
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}
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nums[i] = x;
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return i;
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}
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}

‎src/main/java/cn/byhieg/designpatterntutorial/proxy/dynamicproxy/Client.java‎

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package cn.byhieg.designpatterntutorial.proxy.dynamicproxy;
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import java.lang.reflect.Proxy;
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/**
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* Created by shiqifeng on 2017/3/17.
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* Mail byhieg@gmail.com
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*/
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public class Client {
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public static void main(String[] args) {
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Subject realSubject = new RealSubject();
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DynamicProxy proxy = new DynamicProxy(realSubject);
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ClassLoader classLoader = realSubject.getClass().getClassLoader();
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Subject subject = (Subject) Proxy.newProxyInstance(classLoader, new Class[]{Subject.class}, proxy);
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subject.visit();
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}
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}

‎src/main/java/cn/byhieg/designpatterntutorial/proxy/dynamicproxy/DynamicProxy.java‎

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public class DynamicProxy implements InvocationHandler {
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private Object object;
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public DynamicProxy(Object object) {
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this.object = object;
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}
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@Override
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public Object invoke(Object proxy, Method method, Object[] args) throws Throwable {
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Object result = method.invoke(object, args);

‎src/main/java/cn/byhieg/designpatterntutorial/proxy/dynamicproxy/RealSubject.java‎

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package cn.byhieg.designpatterntutorial.proxy.dynamicproxy;
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/**
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* Created by shiqifeng on 2017/3/17.
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* Mail byhieg@gmail.com
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*/
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public class RealSubject implements Subject {
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private String name = "byhieg";
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@Override
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public void visit() {
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System.out.println(name);
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}
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}

‎src/main/java/cn/byhieg/designpatterntutorial/proxy/dynamicproxy/Subject.java‎

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package cn.byhieg.designpatterntutorial.proxy.dynamicproxy;
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/**
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* Created by shiqifeng on 2017/3/17.
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* Mail byhieg@gmail.com
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*/
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public interface Subject {
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void visit();
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}

‎src/test/java/cn/byhieg/algorithmtutorialtest/SortTest.java‎

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package cn.byhieg.algorithmtutorialtest;
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import cn.byhieg.algorithmtutorial.Sort;
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import junit.framework.TestCase;
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/**
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* Created by shiqifeng on 2017/3/28.
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* Mail byhieg@gmail.com
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*/
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public class SortTest extends TestCase {
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int [] nums;
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public void setUp() throws Exception {
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super.setUp();
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nums = new int[]{10, 20, 2, 3, 1, 100, 45, 22, 51, 21};
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}
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public void tearDown() throws Exception {
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for (int i = 0 ; i < nums.length;i++){
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System.out.print(nums[i] + " ");
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}
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}
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// public void testChooseSort() throws Exception {
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// new Sort().chooseSort(nums);
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// }
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// public void testInsertDirectlySort() throws Exception {
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// new Sort().insertDirectlySort(nums);
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// }
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// public void testInsertBinarySort() throws Exception {
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// new Sort().insertBinarySort(nums);
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// }
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// public void testBubbleSort() throws Exception {
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// new Sort().bubbleSort2(nums);
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// }
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public void testQuickSort() throws Exception {
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new Sort().quickSort(nums);
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}
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}

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