K-means聚類
阿新 • • 發佈:2021-10-02
堆排序在是建立在完全二叉樹上的排序模型,在計算機中使用陣列實現。
背景知識:
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完全二叉樹:除最後一層節點外,其他層節點都必須要有兩個子節點,並且最後一層節點都要左排列
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大根堆:每個結點的值都大於或等於其左右孩子結點的值
** 堆的儲存**
我們預設使用陣列的1位置為起始位置,
下標為 i
的結點的父結點為 (i - 1)/2
; 左子結點(2i + 1)
右子結點(2i + 2)
核心程式碼
public static void heapSort(int[] arr) { if (arr == null || arr.length < 2) { return; } for (int i = 0; i < arr.length; i++) { heapInsert(arr, i); } int size = arr.length; swap(arr, 0, --size); while (size > 0) { heapify(arr, 0, size); swap(arr, 0, --size); } } public static void heapInsert(int[] arr, int index) { while (arr[index] > arr[(index - 1) / 2]) { swap(arr, index, (index - 1) /2); index = (index - 1)/2 ; } } public static void heapify(int[] arr, int index, int size) { int left = index * 2 + 1; while (left < size) { int largest = left + 1 < size && arr[left + 1] > arr[left] ? left + 1 : left; largest = arr[largest] > arr[index] ? largest : index; if (largest == index) { break; } swap(arr, largest, index); index = largest; left = index * 2 + 1; } } public static void swap(int[] arr, int i, int j) { int tmp = arr[i]; arr[i] = arr[j]; arr[j] = tmp; }
全部程式碼
package class02; import java.util.Arrays; public class Code03_HeapSort { public static void heapSort(int[] arr) { if (arr == null || arr.length < 2) { return; } for (int i = 0; i < arr.length; i++) { heapInsert(arr, i); } int size = arr.length; swap(arr, 0, --size); while (size > 0) { heapify(arr, 0, size); swap(arr, 0, --size); } } public static void heapInsert(int[] arr, int index) { while (arr[index] > arr[(index - 1) / 2]) { swap(arr, index, (index - 1) /2); index = (index - 1)/2 ; } } public static void heapify(int[] arr, int index, int size) { int left = index * 2 + 1; while (left < size) { int largest = left + 1 < size && arr[left + 1] > arr[left] ? left + 1 : left; largest = arr[largest] > arr[index] ? largest : index; if (largest == index) { break; } swap(arr, largest, index); index = largest; left = index * 2 + 1; } } public static void swap(int[] arr, int i, int j) { int tmp = arr[i]; arr[i] = arr[j]; arr[j] = tmp; } // for test public static void comparator(int[] arr) { Arrays.sort(arr); } // for test public static int[] generateRandomArray(int maxSize, int maxValue) { int[] arr = new int[(int) ((maxSize + 1) * Math.random())]; for (int i = 0; i < arr.length; i++) { arr[i] = (int) ((maxValue + 1) * Math.random()) - (int) (maxValue * Math.random()); } return arr; } // for test public static int[] copyArray(int[] arr) { if (arr == null) { return null; } int[] res = new int[arr.length]; for (int i = 0; i < arr.length; i++) { res[i] = arr[i]; } return res; } // for test public static boolean isEqual(int[] arr1, int[] arr2) { if ((arr1 == null && arr2 != null) || (arr1 != null && arr2 == null)) { return false; } if (arr1 == null && arr2 == null) { return true; } if (arr1.length != arr2.length) { return false; } for (int i = 0; i < arr1.length; i++) { if (arr1[i] != arr2[i]) { return false; } } return true; } // for test public static void printArray(int[] arr) { if (arr == null) { return; } for (int i = 0; i < arr.length; i++) { System.out.print(arr[i] + " "); } System.out.println(); } // for test public static void main(String[] args) { int testTime = 500000; int maxSize = 100; int maxValue = 100; boolean succeed = true; for (int i = 0; i < testTime; i++) { int[] arr1 = generateRandomArray(maxSize, maxValue); int[] arr2 = copyArray(arr1); heapSort(arr1); comparator(arr2); if (!isEqual(arr1, arr2)) { succeed = false; break; } } System.out.println(succeed ? "Nice!" : "Fucking fucked!"); int[] arr = generateRandomArray(maxSize, maxValue); printArray(arr); heapSort(arr); printArray(arr); } }