各种排序算法知识总结
今天学习了各种各样的排序算法，来做个总结吧
首先，算法很重要的指标是时间复杂度，其中，冒泡排序，插入排序，选择排序的时间复杂度为O(N^2)，快速排序、归并排序、堆排序、希尔排序的时间复杂度是O(NlogN)
选择排序 堆排序 快速排序 希尔排序 是不稳定的，其他都是稳定的
经典排序算法，空间复杂度为O(1)的有冒泡 选择 插入 希尔 堆
为O(logN)~O(N)的有快速排序
为O(N)的有归并排序
下面给一些算法的例子，自己写的哦~
- 冒泡排序
public class BubbleSort {
public static void bubbleSort(int[] arr) {
if (arr == null || arr.length < 2) {
return;
}
for (int i = arr.length - 1; i >= 0; i--) {
for (int j = 0; j < i; j++) {
if (arr[j] > arr[j + 1]) {
swap(arr, j, j + 1);
}
}
}
}
public static void swap(int[] arr, int index1, int index2) {
int tmp = arr[index1];
arr[index1] = arr[index2];
arr[index2] = tmp;
}
public static int[] generateArray(int len, int range) {
if (len < 1) {
return null;
}
int[] arr = new int[len];
for (int i = 0; i < len; i++) {
arr[i] = (int) (Math.random() * range);
}
return arr;
}
public static void printArray(int[] arr) {
if (arr == null || arr.length == 0) {
return;
}
for (int i = 0; i < arr.length; i++) {
System.out.print(arr[i] + " ");
}
System.out.println();
}
public static boolean isSorted(int[] arr) {
if (arr == null || arr.length < 2) {
return true;
}
for (int i = 1; i < arr.length; i++) {
if (arr[i - 1] > arr[i]) {
return false;
}
}
return true;
}
public static void main(String[] args) {
int len = 10;
int range = 10;
int testTimes = 50000;
for (int i = 0; i < testTimes; i++) {
int[] arr = generateArray(len, range);
bubbleSort(arr);
if (!isSorted(arr)) {
System.out.println("Wrong Case:");
printArray(arr);
break;
}
}
int len2 = 13;
int range2 = 10;
int testTimes2 = 50000;
for (int i = 0; i < testTimes2; i++) {
int[] arr = generateArray(len2, range2);
bubbleSort(arr);
if (!isSorted(arr)) {
System.out.println("Wrong Case:");
printArray(arr);
break;
}
}
}
}- 选择排序
public class SelectionSort {
public static void selectSort(int[] arr) {
if (arr == null || arr.length < 2) {
return;
}
int mini = 0;
for (int i = 0; i < arr.length - 1; i++) {
mini = i;
for (int j = i + 1; j < arr.length; j++) {
mini = arr[mini] > arr[j] ? j : mini;
}
swap(arr, i, mini);
}
}
public static void swap(int[] arr, int index1, int index2) {
int tmp = arr[index1];
arr[index1] = arr[index2];
arr[index2] = tmp;
}
public static int[] generateArray(int len, int range) {
if (len < 1) {
return null;
}
int[] arr = new int[len];
for (int i = 0; i < len; i++) {
arr[i] = (int) (Math.random() * range);
}
return arr;
}
public static void printArray(int[] arr) {
if (arr == null || arr.length == 0) {
return;
}
for (int i = 0; i < arr.length; i++) {
System.out.print(arr[i] + " ");
}
System.out.println();
}
public static boolean isSorted(int[] arr) {
if (arr == null || arr.length < 2) {
return true;
}
for (int i = 1; i < arr.length; i++) {
if (arr[i - 1] > arr[i]) {
return false;
}
}
return true;
}
public static void main(String[] args) {
int len = 10;
int range = 10;
int testTimes = 50000;
for (int i = 0; i < testTimes; i++) {
int[] arr = generateArray(len, range);
selectSort(arr);
if (!isSorted(arr)) {
System.out.println("Wrong Case:");
printArray(arr);
break;
}
}
int len2 = 13;
int range2 = 10;
int testTimes2 = 50000;
for (int i = 0; i < testTimes2; i++) {
int[] arr = generateArray(len2, range2);
selectSort(arr);
if (!isSorted(arr)) {
System.out.println("Wrong Case:");
printArray(arr);
break;
}
}
}
}- 插入排序
public class InsertionSort {
public static void insertionSort(int[] arr) {
if (arr == null || arr.length < 2) {
return;
}
int index = 0;
for (int i = 1; i < arr.length; i++) {
index = i;
while (index > 0) {
if (arr[index - 1] > arr[index]) {
swap(arr, index - 1, index);
index--;
} else {
break;
}
}
}
}
public static void swap(int[] arr, int index1, int index2) {
int tmp = arr[index1];
arr[index1] = arr[index2];
arr[index2] = tmp;
}
public static int[] generateArray(int len, int range) {
if (len < 1) {
return null;
}
int[] arr = new int[len];
for (int i = 0; i < len; i++) {
arr[i] = (int) (Math.random() * range);
}
return arr;
}
public static void printArray(int[] arr) {
if (arr == null || arr.length == 0) {
return;
}
for (int i = 0; i < arr.length; i++) {
System.out.print(arr[i] + " ");
}
System.out.println();
}
public static boolean isSorted(int[] arr) {
if (arr == null || arr.length < 2) {
return true;
}
for (int i = 1; i < arr.length; i++) {
if (arr[i - 1] > arr[i]) {
return false;
}
}
return true;
}
public static void main(String[] args) {
int len = 10;
int range = 10;
int testTimes = 50000;
for (int i = 0; i < testTimes; i++) {
int[] arr = generateArray(len, range);
insertionSort(arr);
if (!isSorted(arr)) {
System.out.println("Wrong Case:");
printArray(arr);
break;
}
}
int len2 = 13;
int range2 = 10;
int testTimes2 = 50000;
for (int i = 0; i < testTimes2; i++) {
int[] arr = generateArray(len2, range2);
insertionSort(arr);
if (!isSorted(arr)) {
System.out.println("Wrong Case:");
printArray(arr);
break;
}
}
}
}
- 归并排序
public class MergeSort {
public int[] mergeSort(int[] A, int n) {
// write code here
process(A,0,n-1);
return A;
}
private void process(int[] arr, int left, int right) {
// TODO Auto-generated method stub
if (left == right) {
return;
}
int mid = (left+right)/2;
process(arr,left,mid);
process(arr,mid+1,right);
merge(arr,left,mid,right);
}
private void merge(int[] arr, int left, int mid, int right) {
// TODO Auto-generated method stub
int[] help = new int[right - left + 1];
int l = left;
int r = mid + 1;
int index = 0;
while (l <= mid && r <= right) {
if (arr[l] <= arr[r]) {
help[index++] = arr[l++];
} else {
help[index++] = arr[r++];
}
}
while (l <= mid) {
help[index++] = arr[l++];
}
while (r <= right) {
help[index++] = arr[r++];
}
for (int i = 0; i < help.length; i++) {
arr[left + i] = help[i];
}
}
public static void printArray(int[] arr) {
if (arr == null || arr.length == 0) {
return;
}
for (int i = 0; i < arr.length; i++) {
System.out.print(arr[i] + " ");
}
System.out.println();
}
public static void main(String[] args) {
int[] arr = new int[]{54,35,48,36,27,12,44,44,8,14,26,17,28};
MergeSort ms = new MergeSort();
int[] arr2 = ms.mergeSort(arr, 13);
printArray(arr2);
}
}- 快速排序
public class QuickSort {
public int[] quickSort(int[] A, int n) {
// write code here
process(A, 0, n - 1);
return A;
}
private void process(int[] arr, int left, int right) {
// TODO Auto-generated method stub
if (leftint random = left + (int)(Math.random()*(right-left+1));
swap(arr,random,right);
int mid = partition(arr,left,right);
process(arr,left,mid-1);
process(arr,mid+1,right);
}
}
private int partition(int[] arr, int left, int right) {
// TODO Auto-generated method stub
int pivot = left-1;
int index = left;
while (index<=right) {
if (arr[index]<=arr[right]) {
swap(arr,++pivot,index);
}
index++;
}
return pivot;
}
private void swap(int[] arr, int index1, int index2) {
// TODO Auto-generated method stub
int tmp = arr[index1];
arr[index1] = arr[index2];
arr[index2] = tmp;
}
public static void printArray(int[] arr) {
if (arr == null || arr.length == 0) {
return;
}
for (int i = 0; i < arr.length; i++) {
System.out.print(arr[i] + " ");
}
System.out.println();
}
public static void main(String[] args) {
int[] arr = new int[]{54,35,48,36,27,12,44,44,8,14,26,17,28};
QuickSort ms = new QuickSort();
ms.quickSort(arr, 13);
printArray(arr);
}
}
- 希尔排序
public class ShellSort {
public int[] shellSort(int[] A, int n) {
// write code here
int feet = n/2;
int index = 0;
while(feet>0){
for (int i = feet; i < A.length; i++) {
index = i;
while(index >= feet){
if (A[index-feet]>A[index]) {
swap(A,index-feet,index);
index -= feet;
}else{
break;
}
}
}
feet /= 2;
}
return A;
}
public static void printArray(int[] arr) {
if (arr == null || arr.length == 0) {
return;
}
for (int i = 0; i < arr.length; i++) {
System.out.print(arr[i] + " ");
}
System.out.println();
}
private void swap(int[] arr, int index1, int index2) {
// TODO Auto-generated method stub
int tmp = arr[index1];
arr[index1] = arr[index2];
arr[index2] = tmp;
}
public static void main(String[] args) {
int[] arr = new int[]{54,35,48,36,27,12,44,44,8,14,26,17,28};
ShellSort ms = new ShellSort();
ms.shellSort(arr, 13);
printArray(arr);
}
}- 堆排序
public class HeapSort {
public int[] heapSort(int[] A, int n) {
// write code here
for (int i = n/2; i >=0; i--) {
heapAdjust(A,i,n);
}
for (int i = n-1; i > 0; i--) {
swap(A,0,i);
heapAdjust(A,0,i);
}
return A;
}
private void heapAdjust(int[] A, int index, int length) {
// TODO Auto-generated method stub
int childLeft;
int temp = A[index];
for( ;index*2+1 < length;index = childLeft){
childLeft = index*2+1;
if(childLeft !=length-1 && A[childLeft] < A[childLeft+1]){
childLeft++;
}
if(temp > A[childLeft]){
break;
}
else {
A[index] = A[childLeft];
index = childLeft;
}
}
A[index] = temp;
}
public static void printArray(int[] arr) {
if (arr == null || arr.length == 0) {
return;
}
for (int i = 0; i < arr.length; i++) {
System.out.print(arr[i] + " ");
}
System.out.println();
}
private void swap(int[] arr, int index1, int index2) {
// TODO Auto-generated method stub
int tmp = arr[index1];
arr[index1] = arr[index2];
arr[index2] = tmp;
}
public static void main(String[] args) {
int[] arr = new int[]{54,35,48,36,27,12,44,44,8,14,26,17,28};
HeapSort ms = new HeapSort();
ms.heapSort(arr, 13);
printArray(arr);
}
}