5種java排序算法彙總工具類

工具類簡單明了地總結了java的快速排序，希爾排序，插入排序，堆排序，歸併排序五種排序算法，代碼中並沒有對這幾種排序算法的一個說明，關於思想部分希望在自行查閱相關說明，這裡只是對這幾種算法進行一個概括，以供大家使用。

 public class Sort { public static <AnyType extends Comparable<? super AnyType>> void insertionSort(AnyType[] a) { insertionSort(a, 0, a.length - 1); } private static <AnyType extends Comparable<? super AnyType>> void insertionSort(AnyType[] a, int left, int right) { int j; // 記錄第一個比tmp小的元素的後邊一位的位置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 <AnyType extends Comparable<? super AnyType>> 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 <AnyType extends Comparable<? super AnyType>> 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 <AnyType extends Comparable<? super AnyType>> 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 <AnyType extends Comparable<? super AnyType>> void swapReferences(AnyType[] arr, int i, int j) { AnyType tmp = arr[i]; arr[i] = arr[j]; arr[j] = tmp; } public static <AnyType extends Comparable<? super AnyType>> void mergeSort(AnyType[] arr) { AnyType[] tmp = ((AnyType[]) new Comparable[arr.length]); mergeSort(arr, 0, arr.length - 1, tmp); } private static <AnyType extends Comparable<? super AnyType>> 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 <AnyType extends Comparable<? super AnyType>> 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 <AnyType extends Comparable<? super AnyType>> void quickSort(AnyType[] arr) { quickSort(arr, 0, arr.length - 1); } private static <AnyType extends Comparable<? super AnyType>> 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 extends Comparable<? super AnyType>> 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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