1、冒泡排序（Bubble Sort）
public class BubbleSort {
public static void main(String[] args) {
int[] arr = {3, 4, 2, 9, 10, 15, 11, 0, 1};
System.out.println(Arrays.toString(bubbleSort(arr)));
}
public static int[] bubbleSort(int[] arr){
for (int i = 0; i < arr.length - 1; i++) {
for(int j = 0; j < arr.length - 1 - i; j++){
if(arr[j] > arr[j + 1]){
int temp = arr[j + 1];
arr[j + 1] = arr[j];
arr[j] = temp;
}
}
}
return arr;
}
}
2、選擇排序（Selection Sort）
public class SelectionSort {
public static void main(String[] args) {
int[] arr = {3, 4, 2, 9, 10, 15, 11, 0, 1};
System.out.println(Arrays.toString(selectionSort(arr)));
}
public static int[] selectionSort(int[] arr){
for (int i = 0; i < arr.length - 1; i++) {
int minIndex = i;
for (int j = i + 1; j < arr.length; j++) {
if(arr[minIndex] > arr[j]){
minIndex = j;
}
}
//交換
int temp = arr[minIndex];
arr[minIndex] = arr[i];
arr[i] = temp;
}
return arr;
}
}
3、插入排序（Insertion Sort）
public class InsertionSort {
public static void main(String[] args) {
int[] arr = {3, 4, 2, 9, 10, 15, 11, 0, 1};
System.out.println(Arrays.toString(insertionSort(arr)));
}
public static int[] insertionSort(int[] arr) {
int current, preIndex;
for (int i = 1; i < arr.length; i++) {
current = arr[i];
preIndex = i - 1;
while(preIndex >= 0 && current < arr[preIndex]){
arr[preIndex + 1] = arr[preIndex];
preIndex --;
}
arr[preIndex + 1] = current;
}
return arr;
}
}
4、希爾排序（Shell Sort）
public class ShellSort {
public static void main(String[] args) {
int[] arr = {80, 30, 60, 40, 20, 10, 50, 70};
System.out.println(Arrays.toString(shellSort(arr)));
}
public static int[] shellSort(int[] arr){
int len = arr.length;
for (int gap = len / 2; gap > 0; gap /= 2) {//設置步長
for (int i = gap; i < len ; i++) {
int j = i;
int temp = arr[i];
while(j - gap >= 0 && temp < arr[j - gap]){
arr[j] = arr[j - gap];
j -= gap;
}
arr[j] = temp;
}
}
return arr;
}
}
5、歸併排序（Merge Sort）
public class MergeSort {
public static void main(String[] args) {
int[] arr = {10, 8, 1, 4, 5, 3, 2, 9, 10, 22, 8};
int[] temp = new int[arr.length];
int[] arr2 = mergeSort(arr, 0, arr.length - 1, temp);
System.out.println(Arrays.toString(arr2));
}
/**
* 歸併排序
*
* @param arr
* @param left
* @param right
*/
public static int[] mergeSort(int[] arr, int left, int right, int[] temp) {
if (left < right) {
int mid = (left + right) / 2;
//向左分解
mergeSort(arr, left, mid, temp);
//向右分解
mergeSort(arr, mid + 1, right, temp);
//合併
merge(arr, left, mid, right, temp);
}
return arr;
}
/**
* 合併
*
* @param arr 原數組
* @param left 左指針
* @param mid 中指針
* @param right 右指針
* @param temp 中間數組
*/
public static void merge(int[] arr, int left, int mid, int right, int[] temp) {
int i = left, j = mid + 1, k = 0;
//比較數據大小，從小到大放入temp中
while (i <= mid && j <= right) {
if (arr[i] < arr[j]) {
temp[k] = arr[i];
k++;
i++;
} else {
temp[k] = arr[j];
k++;
j++;
}
}
//判斷arr中是否有剩餘數據
while (i <= mid) {
temp[k] = arr[i];
k++;
i++;
}
while (j <= right) {
temp[k] = arr[j];
k++;
j++;
}
k = 0;
int c = left;
//將排好序的temp賦給arr
while (c <= right) {
arr[c] = temp[k];
k++;
c++;
}
}
}
6、快速排序（Quick Sort）
public class QuickSort {
public static void main(String[] args) {
int[] arr = {4, 6, 7, 0, -1, 2, -4};
int[] arr2 = quickSort(arr, 0, arr.length - 1);
System.out.println(Arrays.toString(arr2));
}
private static int[] quickSort(int[] arr, int left, int right) {
int l = left;
int r = right;
int pivot = arr[(l + r) / 2];
int temp;
while(l < r){
while(arr[l] < pivot){
l++;
}
while(arr[r] > pivot){
r--;
}
if(l >= r){
break;
}
//交換
temp = arr[l];
arr[l] = arr[r];
arr[r] = temp;
if(arr[l] == pivot){
r--;
}
if(arr[r] == pivot){
l++;
}
}
if(l == r){
l++;
r--;
}
if(r > left){
quickSort(arr, left, r);
}
if(l < right){
quickSort(arr, l, right);
}
return arr;
}
}
7、堆排序（Heap Sort）
public class HeapSort {
public static void main(String[] args) {
int[] arr = {4, 6, 7, 0, -1, 2, -4};
System.out.println(Arrays.toString(heapSort(arr)));
}
public static int[] heapSort(int[] arr) {
//以最後一個非葉子結點構建大頂堆
for (int i = arr.length / 2 - 1; i >= 0; i--) {
adjustHeap(arr, i, arr.length);
}
//此時頂部元素是最大的，交換頂部元素和末端元素
for (int i = arr.length - 1; i > 0; i--) {
swap(arr, 0, i);
//末端元素已是最大的了，無需考慮排序
adjustHeap(arr, 0, i);
}
return arr;
}
public static void adjustHeap(int[] arr, int i, int len) {
//保存當前結點
int temp = arr[i];
//遍歷當前結點的左子結點
for (int k = 2 * i + 1; k < len; k = 2 * k + 1) {
//若是右結點存在 且 右結點比左結點大，指向右結點
if (k + 1 < len && arr[k] < arr[k + 1]) {
k++;
}
//判斷當前結點和左（右）結點哪一個大
if (temp < arr[k]) {
//交換
swap(arr, k, i);
//交換後，下次遍歷以該子結點做爲根節點的子樹就會受到影響，所以須要從新指定下次的根節點
i = k;
} else {
//不用交換，直接終止循環
break;
}
}
}
public static void swap(int[] arr, int i, int j) {
int temp = arr[i];
arr[i] = arr[j];
arr[j] = temp;
}
}
8、計數排序（Counting Sort）
public class CountingSort {
public static void main(String[] args) {
int[] arr = {4, 6, 7, 0, 1, 2, 4, 1, 7};
System.out.println(Arrays.toString(countingSort(arr)));
}
public static int[] countingSort(int[] arr) {
int max = arr[0];
int sortIndex = 0;
//找到最大值
for (int i = 1; i < arr.length; i++) {
if (arr[i] > max) {
max = arr[i];
}
}
int[] bucket = new int[max + 1];
//將待排序數組的值做爲新數組的下標，新數組的下標對應的值就是這個數的個數，
// 所以待排序數組不能有負數
for (int i = 0; i < arr.length; i++) {
bucket[arr[i]]++;
}
// System.out.println("新數組："+Arrays.toString(bucket));
//將新數組的值從新賦給待排序數組
for (int i = 0; i < bucket.length; i++) {
while (bucket[i] > 0) {
arr[sortIndex++] = i;
bucket[i]--;
}
}
return arr;
}
}
9、桶排序（Bucket Sort）
public class BucketSort {
public static void main(String[] args) {
int[] arr = {4, 6, 7, 0, 1, 2, 4, 1, 7};
System.out.println(Arrays.toString(bucketSort(arr)));
}
public static int[] bucketSort(int[] arr) {
int min = arr[0], max= arr[0];
//找到最大值最小值
for (int i = 0; i < arr.length; i++) {
if(arr[i] < min){
min = arr[i];
}
if(arr[i] > max){
max = arr[i];
}
}
int d = max - min;
int bucketCount = d / 5 + 1; //桶的個數
ArrayList<LinkedList<Integer>> bucket = new ArrayList<>();
//初始化
for (int i = 0; i < bucketCount; i++) {
bucket.add(new LinkedList<Integer>());
}
//遍歷待排序數組，將數據放入集合中
for (int i = 0; i < arr.length; i++) {
bucket.get((arr[i] - min) / d).add(arr[i] - min);
}
//對每一個桶裏的元素排序
for (int i = 0; i < bucketCount; i++) {
Collections.sort(bucket.get(i));
}
//將集合的數據放到原數組裏
int k = 0;
for (int i = 0; i < bucketCount; i++) {
for (Integer num : bucket.get(i)) {
arr[k++] = num + min;
}
}
return arr;
}
}
10、基數排序（Radix Sort）
public class RadixSort {
public static void main(String[] args) {
int[] arr = {3, 4, 2, 9, 10, 15, 11, 0, 1};
System.out.println(Arrays.toString(radixSort(arr)));
}
public static int[] radixSort(int[] arr) {
int max = arr[0], n = arr.length;
//找到最大數
for (int i = 1; i < n; i++) {
if(max < arr[i]){
max = arr[i];
}
}
//判斷max是幾位數
int num = 1;
while(max / 10 > 0){
num++;
max /= 10;
}
//建立10個桶
ArrayList<LinkedList<Integer>> bucket = new ArrayList<>(10);
//初始化
for (int i = 0; i < 10; i++) {
bucket.add(new LinkedList<>());
}
//遍歷原數組，將數據按規則放到桶中
//從個位開始
for (int i = 1; i <= num; i++) {
//按照數據位數的數字放到桶中
for (int j = 0; j < n; j++) {
//獲取數字個位、十位....上的數字
int radix = (arr[j] / (int) Math.pow(10, i - 1)) % 10;
bucket.get(radix).add(arr[j]);
}
//將數據放回原數組
int k = 0;
for (int j = 0; j < 10; j++) {
for(int t : bucket.get(j)){
arr[k++] = t;
}
//清空桶的數據
bucket.get(j).clear();
}
}
return arr;
}
}