java五种排序算法

时间:2024-07-18 15:53:07 JAVA认证 我要投稿
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java五种排序算法汇总

  java的排序算法工具有哪些?这个工具类简单明了地总结了java的快速排序,希尔排序,插入排序,堆排序,归并排序五种排序算法,代码中并没有对这几种排序算法的一个说明,关于思想部分希望在自行查阅相关说明,这里只是对这几种算法进行一个概括,以供大家使用。

  private static > void insertionSort(AnyType[] a, int left, int right) {

  int j; // 记录第一个比tmp小的元素的后边一位的位置

  for (int p = left; p <= right; p++) {

  AnyType tmp = a[p];

  for (j = p; j > left && tmp.compareTo(a[j - 1]) < 0; j--) {

  a[j] = a[j - 1];

  }

  a[j] = tmp;

  }

  }

  public static > void shellSort(AnyType[] arr) {

  int j;

  for (int gap = arr.length / 2; gap > 0; gap /= 2) {

  for (int i = gap; i < arr.length; i++) {

  AnyType tmp = arr[i];

  for (j = i; j >= gap && tmp.compareTo(arr[j - gap]) < 0; j -= gap) {

  arr[j] = arr[j - gap];

  }

  arr[j] = tmp;

  }

  }

  }

  private static int leftChild(int i) {

  return i * 2 + 1;

  }

  private static > void perculateDown(AnyType[] arr, int i, int size) {

  AnyType tmp = arr[i];

  for (int child; (child = leftChild(i)) < size; i = child) {

  if (child != size - 1 && arr[child].compareTo(arr[child + 1]) < 0) {

  child++;

  }

  if (tmp.compareTo(arr[child]) < 0) {

  arr[i] = arr[child];

  } else {

  break;

  }

  }

  arr[i] = tmp;

  }

  public static > void heapSort(AnyType[] arr) {

  for (int i = arr.length / 2; i >= 0; i--) {

  perculateDown(arr, i, arr.length);

  }

  for (int i = arr.length - 1; i >= 0; i--) {

  swapReferences(arr, 0, i);

  perculateDown(arr, 0, i);

  }

  }

  private static > void swapReferences(AnyType[] arr, int i, int j) {

  AnyType tmp = arr[i];

  arr[i] = arr[j];

  arr[j] = tmp;

  }

  public static > void mergeSort(AnyType[] arr) {

  AnyType[] tmp = ((AnyType[]) new Comparable[arr.length]);

  mergeSort(arr, 0, arr.length - 1, tmp);

  }

  private static > void mergeSort(AnyType[] arr, int start, int end, AnyType[] tmp) {

  if (start < end) {

  int mid = (start + end) >> 1;

  mergeSort(arr, start, mid, tmp);

  mergeSort(arr, mid + 1, end, tmp);

  merge(arr, start, mid, end, tmp);

  }

  }

  private static > void merge(AnyType[] arr, int start, int mid, int end, AnyType[] tmp) {

  int i = start, j = mid + 1, k = start;

  while (i <= mid && j <= end) {

  if (arr[i].compareTo(arr[j]) < 0) {

  tmp[k++] = arr[i++];

  } else {

  tmp[k++] = arr[j++];

  }

  }

  while (i <= mid) {

  tmp[k++] = arr[i++];

  }

  while (j <= end) {

  tmp[k++] = arr[j++];

  }

  for (int m = start; m <= end; m++) {

  arr[m] = tmp[m];

  }

  }

  public static > void quickSort(AnyType[] arr) {

  quickSort(arr, 0, arr.length - 1);

  }

  private static > void quickSort(AnyType[] arr, int left, int right) {

  if (left + LENGTH_DIFF <= right) {

  AnyType pivot = medium(arr, left, right);

  int i = left, j = right;

  while (true) {

  while (arr[++i].compareTo(pivot) < 0);

  while (arr[--j].compareTo(pivot) > 0);

  if (i < j) {

  swapReferences(arr, i, j);

  } else {

  break;

  }

  }

  swapReferences(arr, i, right);

  quickSort(arr, left, i - 1);

  quickSort(arr, i + 1, right);

  } else {

  insertionSort(arr, left, right);

  }

  }

  private static > AnyType medium(AnyType[] arr, int left,

  int right) {

  int center = (left + right) / 2;

  if (arr[center].compareTo(arr[left]) < 0) {

  swapReferences(arr, center, left);

  }

  if (arr[left].compareTo(arr[right]) > 0) {

  swapReferences(arr, left, right);

  }

  if (arr[center].compareTo(arr[right]) < 0) {

  swapReferences(arr, center, right);

  }

  return arr[right];

  }

  private final static int LENGTH_DIFF = 20;

  }

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