「博客搬家」 原地址: 原发表时间: 2017-08-17
网上有很多排序算法的总结，不过有很多缺点，比如有些根本就是错的，无法通过测试用例，有些过于冗长。所以我总结了一套短小精悍的 Java 实现，经测试，该套实现可通过牛客网的关于此的所有测试用例。
1. 冒泡排序
public class BubbleSort implements KySort { public void kySort(int[] a, int size) { for (int i = 0; i < size - 1; i++) { for (int j = 0; j < size - i - 1; j++) { if (a[j] > a[j + 1]) { swap(a, j, j + 1); } } } }} 2. 插入排序
public class InsertSort implements KySort { public void kySort(int[] a, int size) { for (int i = 1; i < size; i++) { int temp = a[i]; int j = i; while (j > 0 && a[j - 1] > temp) { a[j] = a[j - 1]; j--; } a[j] = temp; } }} 3. 选择排序
public class SelectSort implements KySort { public void kySort(int[] a, int size) { for (int i = 0; i < size - 1; i++) { int min = i; for (int j = i + 1; j < size; j++) { if (a[j] < a[min]) { min = j; } } if (i != min) { swap(a, i, min); } } }} 4. 堆排序
public class HeapSort implements KySort { public void kySort(int[] a, int n) { for (int i = n / 2; i >= 0; i--) { heapAdjust(a, i, n - 1); } for (int i = n - 1; i > 0; i--) { swap(a, 0, i); heapAdjust(a, 0, i - 1); } } /** * @param index 父节点索引 * @param n 尾节点索引 */ private void heapAdjust(int[] a, int index, int n) { int temp = a[index]; for (int child = index * 2 + 1; child <= n; child = index * 2 + 1) { if (child < n && a[child] < a[child + 1]) { child++; } if (temp > a[child]) break; a[index] = a[child]; index = child; } a[index] = temp; }} 5. 归并排序
public class MergeSort implements KySort { public void kySort(int[] a, int size) { sort(a, 0, size - 1, new int[a.length]); } private void sort(int[] a, int left, int right, int[] temp) { if (left >= right) return; int mid = (left + right) / 2; sort(a, left, mid, temp); sort(a, mid + 1, right, temp); merge(a, left, mid, right, temp); } private void merge(int[] a, int left, int mid, int right, int[] temp) { int k = left; int i = left; int j = mid + 1; while (i <= mid && j <= right) { if (a[i] < a[j]) { temp[k++] = a[i++]; } else { temp[k++] = a[j++]; } } while (i <= mid) { temp[k++] = a[i++]; } while (j <= right) { temp[k++] = a[j++]; } while (left <= right) { a[left] = temp[left]; left++; } }} 6. 快速排序
public class QuickSort implements KySort { @Override public void kySort(int[] a, int size) { quickSort(a, 0, size - 1); } private void quickSort(int[] a, int left, int right) { if (right - left < 2) { if (a[left] > a[right]) swap(a, left, right); return; } int p = middleBy3(a, left, right); quickSort(a, left, p - 1); quickSort(a, p + 1, right); } private int middleBy3(int[] a, int left, int right) { int p = (left + right) / 2; int end = right; if (a[left] > a[p]) swap(a, left, p); if (a[left] > a[right]) swap(a, left, right); if (a[p] > a[right]) swap(a, p, right); int temp = a[p]; swap(a, p, right); while (true) { while (a[++left] < temp) ; while (a[--right] > temp) ; if (left >= right) break; else swap(a, left, right); } swap(a, left, end); return left; }} 7. 附录
7.1 交换方法
public class Util { public static void swap(int[] a, int i, int j) { int k = a[i]; a[i] = a[j]; a[j] = k; }} 7.2 基于策略模式的主程序实现
public class SortMain { private static KySort sorter; private int[] a;//定义一个数组 private SortMain(int... values) { //构造函数 a = values; } public static void main(String[] args) { setSorter(new QuickSort()); SortMain arr; arr = new SortMain(5, 4, 3, 2, 1, 0); arr.display(); arr.kySort(); arr.display(); System.out.println("--------"); arr = new SortMain(54, 35, 48, 36, 27, 12, 44, 44, 8, 14, 26, 17, 28); arr.display(); arr.kySort(); arr.display(); System.out.println("--------"); arr = new SortMain(32, 103, 24, 88, 95, 70, 97, 15, 102, 6, 79, 46, 51, 37, 93, 108, 9, 58, 53, 58, 79, 36, 58, 91, 78, 58, 61, 81); //初始化数组 arr.display(); arr.kySort(); arr.display(); } private static void setSorter(KySort sorter) { SortMain.sorter = sorter; } private void display() { for (int i : a) { //遍历数组中每一个元素 System.out.print(i + " "); //展示 } System.out.println(); } private void kySort() { sorter.kySort(a, a.length); }}