java常用排序

冒泡排序

import java.util.Arrays;public class BubbleSort {private static void sort(int[] array) {for (int i = 0; i < array.length; i++) {for (int j = 0; j < array.length - 1 - i; j++) {if (array[j + 1] < array[j]) {int temp = array[j];array[j] = array[j + 1];array[j + 1] = temp;}}}}public static void main(String[] args) {int[] array = { 2, 7, 8, 3, 1, 6, 9, 0, 5, 4 };BubbleSort.sort(array);System.out.println(Arrays.toString(array));}}

插入排序

import java.util.Arrays;public class Insertsort {public static void insertSort(int[] array) {int i, j;int key;for (i = 1; i < array.length; i++) {j = i;key = array[i];while (j > 0 && key < array[j - 1]) {array[j] = array[j - 1];j--;}array[j] = key;}}public static void main(String[] args) {int[] array = { 2, 7, 8, 3, 1, 6, 9, 0, 5, 4 };insertSort(array);System.out.println(Arrays.toString(array));}}

归并排序

import java.util.Arrays;public class MergeSort {public static void merge(int[] array, int low, int mid, int high) {int[] temp = new int[high - low + 1];int i = low;// 左指针int j = mid + 1;// 右指针int k = 0;// 把较小的数先移到新数组中while (i <= mid && j <= high) {if (array[i] < array[j]) {temp[k++] = array[i++];} else {temp[k++] = array[j++];}}// 把左边剩余的数移入数组while (i <= mid) {temp[k++] = array[i++];}// 把右边边剩余的数移入数组while (j <= high) {temp[k++] = array[j++];}// 把新数组中的数覆盖array数组for (int k2 = 0; k2 < temp.length; k2++) {array[k2 + low] = temp[k2];}}public static int[] sort(int[] array, int low, int high) {int mid = (low + high) / 2;if (low < high) {sort(array, low, mid);sort(array, mid + 1, high);merge(array, low, mid, high);}return array;}// 归并排序的实现public static void main(String[] args) {int[] array = { 2, 7, 8, 3, 1, 6, 9, 0, 5, 4 };MergeSort.sort(array, 0, array.length - 1);System.out.println(Arrays.toString(array));}}

快速排序

import java.util.Arrays;public class QuickSort {public static int partition(int[] array, int low, int high) {int key = array[low];while (low < high) {while (low < high && array[high] >= key) {--high;}array[low] = array[high];while (low < high && array[low] <= key) {++low;}array[high] = array[low];}array[low] = key;return low;}public static void sort(int[] array, int low, int high) {if (low < high) {int pivot = partition(array, low, high);sort(array, low, pivot - 1);sort(array, pivot + 1, high);}}public static void main(String[] args) {int[] array = { 2, 7, 8, 3, 1, 6, 9, 0, 5, 4 };QuickSort.sort(array, 0, array.length - 1);System.out.println(Arrays.toString(array));}}

泛型快速排序

import java.util.Arrays;public class QuickSortE {@FunctionalInterfacepublic interface Comparator<T> {int compare(T o1, T o2);}public static <E> void swap(E[] array, int i, int j) {if (i == j)return;E temp = array[i];array[i] = array[j];array[j] = temp;}public static <E> void quicksort(E[] array, int start, int end, Comparator<E> comparator) {if (end - start <= 0) {return;}int i = start;int j = end - 1;boolean movingI = true;while (i < j) {if (comparator.compare(array[i], array[j]) > 0) {swap(array, i, j);movingI = !movingI;} else {if (movingI) {i++;} else {j--;}}}quicksort(array, start, i, comparator);quicksort(array, i + 1, end, comparator);}public static <E> void quicksort(E[] array, Comparator<E> comparator) {quicksort(array, 0, array.length, comparator);}public static void main(String[] args) {Integer[] array = new Integer[] { 2, 7, 8, 3, 1, 6, 9, 0, 5, 4 };quicksort(array, (a, b) -> a - b);System.out.println(Arrays.toString(array));}}

随机选择枢轴（pivot）快速排序

import java.util.Arrays;public class QuickSortRandomPivot {@FunctionalInterfacepublic interface Comparator<T> {int compare(T o1, T o2);}public static <E> void swap(E[] array, int i, int j) {if (i == j)return;E temp = array[i];array[i] = array[j];array[j] = temp;}public static <E> void quicksort(E[] array, int start, int end, Comparator<E> comparator) {if (end - start <= 0) {return;}int pivotIndex = (int) ((end - start) * Math.random()) + start;swap(array, pivotIndex, end - 1);// let's find the pivot.int i = start;int j = end - 1;boolean movingI = true;while (i < j) {if (comparator.compare(array[i], array[j]) > 0) {swap(array, i, j);movingI = !movingI;} else {if (movingI) {i++;} else {j--;}}}quicksort(array, start, i, comparator);quicksort(array, i + 1, end, comparator);}public static <E> void quicksort(E[] array, Comparator<E> comparator) {quicksort(array, 0, array.length, comparator);}public static void main(String[] args) {Integer[] array = new Integer[] { 2, 7, 8, 3, 1, 6, 9, 0, 5, 4 };quicksort(array, (a, b) -> a - b);System.out.println(Arrays.toString(array));}}