.example-btn{color:#fff;background-color:#5cb85c;border-color:#4cae4c}.example-btn:hover{color:#fff;background-color:#47a447;border-color:#398439}.example-btn:active{background-image:none}div.example{width:98%;color:#000;background-color:#f6f4f0;background-color:#d0e69c;background-color:#dcecb5;background-color:#e5eecc;margin:0 0 5px 0;padding:5px;border:1px solid #d4d4d4;background-image:-webkit-linear-gradient(#fff,#e5eecc 100px);background-image:linear-gradient(#fff,#e5eecc 100px)}div.example_code{line-height:1.4em;width:98%;background-color:#fff;padding:5px;border:1px solid #d4d4d4;font-size:110%;font-family:Menlo,Monaco,Consolas,"Andale Mono","lucida console","Courier New",monospace;word-break:break-all;word-wrap:break-word}div.example_result{background-color:#fff;padding:4px;border:1px solid #d4d4d4;width:98%}div.code{width:98%;border:1px solid #d4d4d4;background-color:#f6f4f0;color:#444;padding:5px;margin:0}div.code div{font-size:110%}div.code div,div.code p,div.example_code p{font-family:"courier new"}pre{margin:15px auto;font:12px/20px Menlo,Monaco,Consolas,"Andale Mono","lucida console","Courier New",monospace;white-space:pre-wrap;word-break:break-all;word-wrap:break-word;border:1px solid #ddd;border-left-width:4px;padding:10px 15px} 排序算法是《数据结构与算法》中最基本的算法之一。排序算法可以分为内部排序和外部排序，内部排序是数据记录在内存中进行排序，而外部排序是因排序的数据很大，一次不能容纳全部的排序记录，在排序过程中需要访问外存。常见的内部排序算法有：插入排序、希尔排序、选择排序、冒泡排序、归并排序、快速排序、堆排序、基数排序等。以下是快速排序算法：
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快速排序是由东尼·霍尔所发展的一种排序算法。在平均状况下，排序 n 个项目要 Ο(nlogn) 次比较。在最坏状况下则需要 Ο(n2) 次比较，但这种状况并不常见。事实上，快速排序通常明显比其他 Ο(nlogn) 算法更快，因为它的内部循环（inner loop）可以在大部分的架构上很有效率地被实现出来。
快速排序使用分治法（Divide and conquer）策略来把一个串行（list）分为两个子串行（sub-lists）。
快速排序又是一种分而治之思想在排序算法上的典型应用。本质上来看，快速排序应该算是在冒泡排序基础上的递归分治法。
快速排序的名字起的是简单粗暴，因为一听到这个名字你就知道它存在的意义，就是快，而且效率高！它是处理大数据最快的排序算法之一了。虽然 Worst Case 的时间复杂度达到了 O(n?)，但是人家就是优秀，在大多数情况下都比平均时间复杂度为 O(n logn) 的排序算法表现要更好，可是这是为什么呢，我也不知道。好在我的强迫症又犯了，查了 N 多资料终于在《算法艺术与信息学竞赛》上找到了满意的答案：
快速排序的最坏运行情况是 O(n?)，比如说顺序数列的快排。但它的平摊期望时间是 O(nlogn)，且 O(nlogn) 记号中隐含的常数因子很小，比复杂度稳定等于 O(nlogn) 的归并排序要小很多。所以，对绝大多数顺序性较弱的随机数列而言，快速排序总是优于归并排序。
1. 算法步骤
从数列中挑出一个元素，称为 "基准"（pivot）;
重新排序数列，所有元素比基准值小的摆放在基准前面，所有元素比基准值大的摆在基准的后面（相同的数可以到任一边）。在这个分区退出之后，该基准就处于数列的中间位置。这个称为分区（partition）操作；
递归地（recursive）把小于基准值元素的子数列和大于基准值元素的子数列排序；
2. 动图演示
代码实现 JavaScript 实例 function quickSort ( arr , left , right ) {
var len = arr. length ,
partitionIndex ,
left = typeof left != 'number' ? 0 : left ,
right = typeof right != 'number' ? len - 1 : right ;
if ( left
这是冒泡排序。
下面是选择排序的代码：
for(int i=0;ia.length;i++){
max = i;
/**查找第 i大的数，直到记下第 i大数的位置***/
for(int j=i+1;ja.length;j++){
if(a[max]a[j])
max = j; //记下较大数位置，再次比较，直到最大
}
/***如果第 i大数的位置不在 i,则交换****/
if(i!=max){
tmp = a[i];
a[i] = a[max];
a[max] = tmp;
}
}
给你介绍4种排序方法及源码，供参考
1.冒泡排序
主要思路： 从前往后依次交换两个相邻的元素，大的交换到后面，这样每次大的数据就到后面，每一次遍历，最大的数据到达最后面，时间复杂度是O(n^2)。
public static void bubbleSort(int[] arr){
for(int i =0; i arr.length - 1; i++){
for(int j=0; j arr.length-1; j++){
if(arr[j] arr[j+1]){
arr[j] = arr[j]^arr[j+1];
arr[j+1] = arr[j]^arr[j+1];
arr[j] = arr[j]^arr[j+1];
}
}
}
}
2.选择排序
主要思路：每次遍历序列，从中选取最小的元素放到最前面，n次选择后，前面就都是最小元素的排列了，时间复杂度是O(n^2）。
public static void selectSort(int[] arr){
for(int i = 0; i arr.length -1; i++){
for(int j = i+1; j arr.length; j++){
if(arr[j] arr[i]){
arr[j] = arr[j]^arr[i];
arr[i] = arr[j]^arr[i];
arr[j] = arr[j]^arr[i];
}
}
}
}
3.插入排序
主要思路：使用了两层嵌套循环，逐个处理待排序的记录。每个记录与前面已经排好序的记录序列进行比较，并将其插入到合适的位置，时间复杂度是O(n^2）。
public static void insertionSort(int[] arr){
int j;
for(int p = 1; p arr.length; p++){
int temp = arr[p]; //保存要插入的数据
//将无序中的数和前面有序的数据相比，将比它大的数，向后移动
for(j=p; j0 temp arr[j-1]; j--){
arr[j] = arr[j-1];
}
//正确的位置设置成保存的数据
arr[j] = temp;
}
}
4.希尔排序
主要思路：用步长分组，每个分组进行插入排序，再慢慢减小步长，当步长为1的时候完成一次插入排序， 希尔排序的时间复杂度是：O（nlogn）～O（n2），平均时间复杂度大致是O(n^1.5)
public static void shellSort(int[] arr){
int j ;
for(int gap = arr.length/2; gap 0 ; gap/=2){
for(int i = gap; i arr.length; i++){
int temp = arr[i];
for(j = i; j=gap temparr[j-gap]; j-=gap){
arr[j] = arr[j-gap];
}
arr[j] = temp;
}
}
}
About this application:
This application implements Straight Selection Sort algorithm which is described like this:
If there are N numbers find the minimum and exchange it with the first number then N numbers remained Continue to find the minimum number in the remained N numbers and exchange it with the second number Repeat this until all the numbers are in order
Note: This is SWT application so you need eclipse swt win win x _ v b jar eclipse jface_ I jar mands_ I jar This is for Eclipse
Source Code:
package selection sort;
import java util ArrayList;
import eclipse swt SWT;
import eclipse swt events KeyAdapter;
import eclipse swt events KeyEvent;
import eclipse swt events ModifyEvent;
import eclipse swt events ModifyListener;
import eclipse swt events SelectionAdapter;
import eclipse swt events SelectionEvent;
import eclipse swt layout FormAttachment;
import eclipse swt layout FormData;
import eclipse swt layout FormLayout;
import eclipse swt widgets Button;
import eclipse swt widgets Display;
import eclipse swt widgets Group;
import eclipse swt widgets Label;
import eclipse swt widgets Shell;
import eclipse swt widgets Text;
/**
* This application implements Straight Selection Sort algorithm which means
* get the minimum number from the numbers and exchange it with the first
* number then doing this for other numbers except the first number Repeat
* this until all numbers are in order If you have any suggestion or problem
* please e mail to
*
* @author vivien Data:
*/
public class StraightSelectionSort {
/** The string containing the number wait for sorted */
public String numString = new String();
public Text numText;
public Text resText;
public Button btSort;
public Label errorLabel;
/** The flag to indicate if there is any error for inputed numbers */
public boolean hasError = false;
/** The arrayList containing the double numbers wait for sorted */
public ArrayListDouble numList = new ArrayListDouble();
public static void main(String[] args) {
StraightSelectionSort selectionSort = new StraightSelectionSort();
selectionSort createControl();
}
/**
* Create the control for the interface
*/
public void createControl() {
Display display = new Display();
Shell shell = new Shell(display);
shell setBounds( );
// Set Title
shell setText( Straight selection sort );
FormLayout layout = new FormLayout();
shell setLayout(layout);
FormData fd = new FormData();
// The Start Sort button
btSort = new Button(shell SWT NONE | SWT CENTER);
btSort setText( Start Sort );
fd = new FormData();
fd height = ;
fd top = new FormAttachment( );
fd left = new FormAttachment( );
btSort setLayoutData(fd);
// The Input numbers group
Group numGroup = new Group(shell SWT NONE);
numGroup setText( Input numbers: );
numGroup setLayout(layout);
fd = new FormData();
fd top = new FormAttachment( );
fd left = new FormAttachment( );
fd right = new FormAttachment( );
fd bottom = new FormAttachment(btSort );
numGroup setLayoutData(fd);
// Label for input numbers
Label numLabel = new Label(numGroup SWT WRAP);
numLabel
setText( Please input the numbers you want to sort: (Note: Numbers need to be seperated by space) );
fd = new FormData();
fd top = new FormAttachment( );
fd left = new FormAttachment( );
fd right = new FormAttachment( );
numLabel setLayoutData(fd);
// Text for input numbers
numText = new Text(numGroup SWT BORDER | SWT MULTI | SWT V_SCROLL
| SWT WRAP);
numText setToolTipText( Numbers need to be seperated by space );
fd = new FormData();
fd top = new FormAttachment(numLabel );
fd left = new FormAttachment( );
fd right = new FormAttachment( );
fd bottom = new FormAttachment( );
numText setLayoutData(fd);
// The results group
Group resGroup = new Group(shell SWT NONE);
resGroup setText( The results: );
resGroup setLayout(layout);
fd = new FormData();
fd top = new FormAttachment(btSort );
fd left = new FormAttachment( );
fd right = new FormAttachment( );
fd bottom = new FormAttachment( );
resGroup setLayoutData(fd);
// Label for results
Label resLabel = new Label(resGroup SWT WRAP);
resLabel
setText( The results after sorted are: (Note: Results are seperated by space) );
fd = new FormData();
fd top = new FormAttachment( );
fd left = new FormAttachment( );
fd right = new FormAttachment( );
resLabel setLayoutData(fd);
// Text for results
resText = new Text(resGroup SWT BORDER | SWT MULTI | SWT V_SCROLL
| SWT WRAP);
resText setToolTipText( Results are seperated by space );
resText setEditable(false);
fd = new FormData();
fd top = new FormAttachment(resLabel );
fd left = new FormAttachment( );
fd right = new FormAttachment( );
fd bottom = new FormAttachment( );
resText setLayoutData(fd);
// Label for showing error message
errorLabel = new Label(shell SWT NONE);
fd = new FormData();
fd top = new FormAttachment( );
fd left = new FormAttachment( );
fd right = new FormAttachment( );
fd bottom = new FormAttachment( );
errorLabel setLayoutData(fd);
errorLabel setForeground(display getSystemColor(SWT COLOR_RED));
// Listen to the numText change
numText addModifyListener(new ModifyListener() {
@Override
public void modifyText(ModifyEvent e) {
numString = numText getText() trim();
hasError = false;
}
});
// If press Return focus go to Start Sort button and start sort
numText addKeyListener(new KeyAdapter() {
@Override
public void keyPressed(KeyEvent e) {
if (e keyCode == \r ) {
e doit = false;
btSort setFocus();
startSort();
}
}
});
// Listen to the button selection
btSort addSelectionListener(new SelectionAdapter() {
public void widgetSelected(SelectionEvent e) {
startSort();
}
});
shell open();
while (!shell isDisposed()) {
if (!display readAndDispatch())
display sleep();
}
display dispose();
}
/**
* Get double values from string
*/
public void getDoubleFromString() {
int index = ;
// Split string using space
String[] splitedNumbers = numString split( );
if (numList size() != )
// Clear the arrayList for last used
numList clear();
for (int i = ; i splitedNumbers length; i++) {
if (splitedNumbers[i] trim() length() != ) {
try {
numList add(index++ Double valueOf(splitedNumbers[i]));
} catch (NumberFormatException e) {
setErrorMessage( Please input the correct numbers );
hasError = true;
break;
}
}
}
}
/**
* Start sort the string containing numbers waited for sort
*/
public void startSort() {
if (numString != null)
if (numString trim() length() != ) {
getDoubleFromString();
startStraightSelectionSort();
setResults();
} else {
setErrorMessage( Please input numbers );
hasError = true;
}
}
/**
* Set the results to the results group
*/
public void setResults() {
if (!hasError) {
String resString = new String();
for (int i = ; i numList size(); i++)
if (i != numList size() )
resString = resString + numList get(i) + ;
else
// If be the last string
resString = resString + numList get(i);
resText setText(resString);
// Clear errorLabel
errorLabel setText( );
}
}
/**
* Sort the numbers using Straight selection Sort algorithm
*/
public void startStraightSelectionSort() {
int minPosition = ;
for (int j = ; j numList size() ; j++) {
minPosition = j;
for (int i = j + ; i numList size(); i++) {
if (numList get(i) numList get(minPosition)) {
minPosition = i;
}
}
if (minPosition != j) {
// Exchange the minimum with the first number of the numbers
// waited for sort
double temp = numList get(j);
numList set(j numList get(minPosition));
numList set(minPosition temp);
}
}
}
/**
* Set the error message on the error Label
*
* @param errorString
* The string used for set on the errorLabel
*/
public void setErrorMessage(String errorString) {
errorLabel setText(errorString);
// Clear the text of results
resText setText( );
hasError = true;
}
}
Black box Test Case:
) All numbers are zero:
