排序算法-堆排序和TopK算法

最小堆排序

从大到小

public class MinHeapSortTest {

    @Test
    public void testQuickSort() {
//        testSort(QuickSort::sort);
        testSort(arr -> MinHeapSortTest.minHeapSort(arr));
    }

    public void testSort(Consumer consumer) {
        int[] result = {1, 2, 3, 4, 5, 6, 7};
        int[] input = {7, 6, 5, 4, 3, 2, 1};
        testSort(consumer, input, result);
        testSort(consumer, new int[]{1, 3, 2, 6, 5, 4, 7}, result);
        testSort(consumer, new int[]{6, 5, 4, 1, 3, 2, 7}, result);
        testSort(consumer, new int[]{1, 3, 6, 5, 4, 2, 7}, result);
        testSort(consumer, new int[]{6, 5, 4, 7, 1, 3, 2}, result);
    }

    public void testSort(Consumer consumer, int[] input, int[] result) {
        System.out.println("src = " + Arrays.toString(input));
        consumer.accept(input);
        // 验证结果
        for (int i = 0; i < result.length; i++) {
            Assert.assertEquals("\ninp = " + Arrays.toString(input) + "\nout = " + Arrays.toString(result), input[i], result[i]);
        }
    }

    /***********************/

    public static void minHeapSort(int[] arr) {
        for (int i = arr.length / 2 - 1; i >= 0; i--) {
            minHeapDown(arr, i, arr.length);
        }
        for (int i = arr.length - 1; i > 0; i--) {
            int tmp = arr[i];
            arr[i] = arr[0];
            arr[0] = tmp;
            minHeapDown(arr, 0, i);
        }

        int r = arr.length - 1;
        int l = 0;
        while (l < r) {
            int tmp = arr[r];
            arr[r] = arr[l];
            arr[l] = tmp;
            r--;
            l++;
        }
    }

    public static void minHeapDown(int[] arr, int i, int len) {
        int tmp = arr[i];
        for (int k = 2 * i + 1; k < len; k = 2 * i + 1) {
            if (k + 1 < len && arr[k + 1] <= arr[k]) {
                k++;
            }
            if (tmp <= arr[k]) {
                break;
            }
            arr[i] = arr[k];
            i = k;
        }
        arr[i] = tmp;
    }
}

最大堆排序

从小到大

public class HeapSort {

    @Test
    public void testQuickSort() {
//        testSort(QuickSort::sort);
        testSort(arr -> HeapSort.heapSort1(arr));
    }

    public void testSort(Consumer consumer) {
        int[] result = {1, 2, 3, 4, 5, 6, 7};
        int[] input = {7, 6, 5, 4, 3, 2, 1};
        testSort(consumer, input, result);
        testSort(consumer, new int[]{1, 3, 2, 6, 5, 4, 7}, result);
        testSort(consumer, new int[]{6, 5, 4, 1, 3, 2, 7}, result);
        testSort(consumer, new int[]{1, 3, 6, 5, 4, 2, 7}, result);
        testSort(consumer, new int[]{6, 5, 4, 7, 1, 3, 2}, result);
    }

    public void testSort(Consumer consumer, int[] input, int[] result) {
        System.out.println("src = " + Arrays.toString(input));
        consumer.accept(input);
        // 验证结果
        for (int i = 0; i < result.length; i++) {
            Assert.assertEquals("\ninp = " + Arrays.toString(input) + "\nout = " + Arrays.toString(result), input[i], result[i]);
        }
    }

    public static void heapSort1(int[] arr) {
        for (int i = arr.length / 2 - 1; i >= 0; i--) {
            heapDown1(arr, i, arr.length);
        }
        for (int j = arr.length - 1; j > 0; j--) {
            int temp = arr[0];
            arr[0] = arr[j];
            arr[j] = temp;
            heapDown1(arr, 0, j);
        }
    }

    public static void heapDown1(int[] arr, int i, int len) {
        int tmp = arr[i];
        for (int k = 2 * i + 1; k < len; k = k * 2 + 1) {
            if (k + 1 < len && arr[k + 1] >= arr[k]) {
                k++;
            }
            if (tmp >= arr[k]) {
                break;
            }
            arr[i] = arr[k];
            i = k;
        }
        arr[i] = tmp;
    }
}

堆排序实现的topK算法

topK算法也可以使用 快速排序算法 实现

public class HeapSortTopK {

    @Test
    public void testSort() {
        testSort(arr -> HeapSortTopK.topK(arr, 3, Integer::compareTo));
    }

    @Test
    public void testSort1() {
        // 取最大的3个值
        List result = HeapSortTopK.topK(Arrays.asList(new Integer[]{1, 3, 6, 5, 4, 2, 7}), 3, (o1, o2) -> o2 - o1);
        System.out.println(result);
    }

    public void testSort(Function, List> function) {
        Integer[] result = {1, 2, 3};
        Integer[] input = {7, 6, 5, 4, 3, 2, 1};
        testSort(function, input, result);
        testSort(function, new Integer[]{1, 3, 2, 6, 5, 4, 7}, result);
        testSort(function, new Integer[]{6, 5, 4, 1, 3, 2, 7}, result);
        testSort(function, new Integer[]{1, 3, 6, 5, 4, 2, 7}, result);
        testSort(function, new Integer[]{6, 5, 4, 7, 1, 3, 2}, result);
    }

    public void testSort(Function, List> function, Integer[] input, Integer[] result) {
        System.out.println("src = " + Arrays.toString(input));
        List returnResult = function.apply(Arrays.asList(input));
        // 验证结果
        Assert.assertTrue(returnResult.size() == result.length);
        for (int i = 0; i < result.length; i++) {
            Assert.assertEquals("\ninp = " + returnResult.toString() + "\nout = " + Arrays.toString(result), returnResult.get(i), result[i]);
        }
    }

     // 取list中最小的topK
    public static  List topK(List list, int topK, Comparator comparator) {
        int len = Math.min(topK, list.size());
        T[] heap = (T[])new Object[len];
        for (int i = 0; i < len; i++) {
            heap[i] = list.get(i);
        }
        initHeap(heap, len, comparator);

        for (int i = len; i < list.size(); i++) {
            T t = list.get(i);
            int compare = comparator.compare(heap[0], t);
            if (compare > 0) {
                heap[0] = t;
                downHeap(heap, 0, len, comparator);
            }
        }

        for (int i = len - 1; i > 0; i--) {
            T tmp = heap[i];
            heap[i] = heap[0];
            heap[0] = tmp;
            downHeap(heap, 0, i, comparator);
        }

        return Arrays.asList(heap);
    }

    public static  void initHeap(T[] heap, int len, Comparator comparator) {
        for (int i = len / 2 - 1; i >= 0; i--) {
            downHeap(heap, i, len, comparator);
        }
    }

    public static  void downHeap(T[] heap, int i, int len, Comparator comparator) {
        T tmp = heap[i];
        for (int k = 2 * i + 1; k < len; k = 2 * k + 1) {
            if (k + 1 < len && comparator.compare(heap[k], heap[k + 1]) <= 0) {
                k++;
            }
            if (comparator.compare(tmp, heap[k]) >= 0) {
                break;
            }
            heap[i] = heap[k];
            i = k;
        }
        heap[i] = tmp;
    }
}