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| 1 | +package grey.algorithm.code11_heap; |
| 2 | + |
| 3 | +import java.io.*; |
| 4 | +import java.util.Arrays; |
| 5 | + |
| 6 | +// 笔记:https://www.cnblogs.com/greyzeng/p/16933830.html |
| 7 | +// 1. 先让整个数组都变成大根堆结构,建立堆的过程: |
| 8 | +// a. 从上到下的方法,时间复杂度为O(N*logN) |
| 9 | +// b. 从下到上的方法,时间复杂度为O(N) |
| 10 | +// 2. 把堆的最大值和堆末尾的值交换, 然后减少堆的大小之后,再去调整堆, 一直周而复始,时间复杂度为O(N*logN) 【扩两倍估算复杂度法】 |
| 11 | +// 3. 把堆的大小减小成0之后,排序完成 |
| 12 | +// 堆排序额外空间复杂度O(1) |
| 13 | +// 测评:https://www.lintcode.com/problem/464 |
| 14 | +//测评链接:https://www.luogu.com.cn/problem/P1177 |
| 15 | +public class Code_0003_HeapSort { |
| 16 | + |
| 17 | + public static void heapSort1(int[] arr) { |
| 18 | + int n = arr.length; |
| 19 | + // O(N*logN) |
| 20 | + for (int i = 0; i < n; i++) { |
| 21 | + heapInsert(arr, i); |
| 22 | + } |
| 23 | + // 注意:这里要保存一个变量,因为n在循环里面会变化 |
| 24 | + int size = n; |
| 25 | + while (size > 0) { |
| 26 | + heapify(arr, 0, size); |
| 27 | + swap(arr, 0, --size); |
| 28 | + } |
| 29 | + } |
| 30 | + |
| 31 | + public static void heapSort2(int[] arr) { |
| 32 | + int n = arr.length; |
| 33 | + // O(N) |
| 34 | + for (int i = n - 1; i >= 0; i--) { |
| 35 | + heapify(arr, i, n); |
| 36 | + } |
| 37 | + // 注意:这里要保存一个变量,因为n在循环里面会变化 |
| 38 | + int size = n; |
| 39 | + while (size > 0) { |
| 40 | + heapify(arr, 0, size); |
| 41 | + swap(arr, 0, --size); |
| 42 | + } |
| 43 | + } |
| 44 | + |
| 45 | + public static void heapInsert(int[] arr, int i) { |
| 46 | + while (arr[i] > arr[(i - 1) / 2]) { |
| 47 | + swap(arr, i, (i - 1) / 2); |
| 48 | + i = (i - 1) / 2; |
| 49 | + } |
| 50 | + } |
| 51 | + |
| 52 | + public static void heapify(int[] arr, int i, int size) { |
| 53 | + int l = 2 * i + 1; |
| 54 | + while (l < size) { |
| 55 | + int best = l + 1 < size && arr[l + 1] > arr[l] ? l + 1 : l; |
| 56 | + best = arr[i] > arr[best] ? i : best; |
| 57 | + if (best == i) { |
| 58 | + break; |
| 59 | + } |
| 60 | + swap(arr, best, i); |
| 61 | + i = best; |
| 62 | + l = 2 * i + 1; |
| 63 | + } |
| 64 | + } |
| 65 | + |
| 66 | + public static void swap(int[] arr, int i, int j) { |
| 67 | + int temp = arr[i]; |
| 68 | + arr[i] = arr[j]; |
| 69 | + arr[j] = temp; |
| 70 | + } |
| 71 | + |
| 72 | + public static void main(String[] args) { |
| 73 | + |
| 74 | + // 数组长度1~500,等概率随机 |
| 75 | + int num = 500; |
| 76 | + // 每个值的大小在1~1024,等概率随机 |
| 77 | + int value = 1024; |
| 78 | + // 测试次数 |
| 79 | + int testTimes = 50000; |
| 80 | + System.out.println("测试开始"); |
| 81 | + for (int i = 0; i < testTimes; i++) { |
| 82 | + int[] arr = generateArray(num, value); |
| 83 | + int[] copyArray = copyArray(arr); |
| 84 | + int[] copyArray2 = copyArray(arr); |
| 85 | + Arrays.sort(arr); |
| 86 | + heapSort1(copyArray); |
| 87 | + heapSort2(copyArray2); |
| 88 | + if (!sameValue(arr, copyArray)) { |
| 89 | + System.out.println("出错了!"); |
| 90 | + break; |
| 91 | + } |
| 92 | + if (!sameValue(arr, copyArray2)) { |
| 93 | + System.out.println("出错了!"); |
| 94 | + break; |
| 95 | + } |
| 96 | + } |
| 97 | + System.out.println("测试结束"); |
| 98 | + } |
| 99 | + |
| 100 | + private static boolean sameValue(int[] arr1, int[] arr2) { |
| 101 | + if (null == arr1) { |
| 102 | + return null != arr2; |
| 103 | + } |
| 104 | + if (null == arr2) { |
| 105 | + return null != arr1; |
| 106 | + } |
| 107 | + if (arr1.length != arr2.length) { |
| 108 | + return false; |
| 109 | + } |
| 110 | + for (int i = 0; i < arr1.length; i++) { |
| 111 | + if (arr1[i] != arr2[i]) { |
| 112 | + return false; |
| 113 | + } |
| 114 | + } |
| 115 | + return true; |
| 116 | + } |
| 117 | + |
| 118 | + private static int[] generateArray(int num, int value) { |
| 119 | + int[] arr = new int[(int) (Math.random() * num) + 1]; |
| 120 | + for (int i = 0; i < arr.length; i++) { |
| 121 | + arr[i] = (int) (Math.random() * value) + 1; |
| 122 | + } |
| 123 | + return arr; |
| 124 | + } |
| 125 | + |
| 126 | + private static int[] copyArray(int[] arr) { |
| 127 | + int[] copyArray = new int[arr.length]; |
| 128 | + for (int i = 0; i < copyArray.length; i++) { |
| 129 | + copyArray[i] = arr[i]; |
| 130 | + } |
| 131 | + return copyArray; |
| 132 | + } |
| 133 | + |
| 134 | +} |
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