几种常用的排序

int[] arr = new int[]{1, 2,8, 7, 5};这是提前准备好的数组

1. 冒泡排序

public static void bubbleSort(int[] arr) {int len = arr.length;for (int i = 0; i < len - 1; i++) {for (int j = 0; j < len - i - 1; j++) {if (arr[j] > arr[j+1]) {int temp = arr[j];arr[j] = arr[j+1];arr[j+1] = temp;}}}
}

1. 选择排序

public static void selectionSort(int[] arr) {int len = arr.length;for (int i = 0; i < len - 1; i++) {int minIndex = i;for (int j = i + 1; j < len; j++) {if (arr[j] < arr[minIndex]) {minIndex = j;}}if (minIndex != i) {int temp = arr[i];arr[i] = arr[minIndex];arr[minIndex] = temp;}}
}

1. 插入排序

public static void insertionSort(int[] arr) {int len = arr.length;for (int i = 1; i < len; i++) {int cur = arr[i];int j = i - 1;while (j >= 0 && arr[j] > cur) {arr[j+1] = arr[j];  j--;}arr[j+1] = cur;}
}

1. 快速排序

public static void quickSort(int[] arr, int left, int right) {if (left >= right) {return;}int pivot = arr[right];int i = left, j = right - 1;while (i <= j) {while (i <= j && arr[i] < pivot) {i++;}while (i <= j && arr[j] >= pivot) {j--;}if (i < j) {int temp = arr[i];arr[i] = arr[j];arr[j] = temp;}} arr[right] = arr[i];arr[i] = pivot;quickSort(arr, left, i - 1);quickSort(arr, i + 1, right);
}

1. 归并排序

public static void mergeSort(int[] arr, int left, int right) {if (left >= right) {return;}int mid = left + (right - left) / 2;mergeSort(arr, left, mid);mergeSort(arr, mid + 1, right);merge(arr, left, mid, right);
}
private static void merge(int[] arr, int left, int mid, int right) {int[] temp = new int[right - left + 1];int i = left, j = mid + 1;int k = 0;while (i <= mid && j <= right) {if (arr[i] <= arr[j]) {temp[k++] = arr[i++];} else {temp[k++] = arr[j++];}}while (i <= mid) {temp[k++] = arr[i++];}while (j <= right) {temp[k++] = arr[j++];}for (int p = 0; p < temp.length; p++) {arr[left + p] = temp[p];}
}

这些排序算法的时间复杂度从O(n^2)到O(nlogn)不等，其中冒泡排序和选择排序为O(n^2)，插入排序和归并排序为O(nlogn)，快速排序的时间复杂度为O(nlogn)。