常用排序算法之堆排序

堆排序算法

/**
     * 堆排序
     *
     * @param array
     * @return
     */
    public static int[] heapSort(int[] array) {
        int arrayLength = array.length;
        for (int i = 0; i < arrayLength - 1; i++) {
            buildMaxHeap(array, arrayLength - 1 - i);
            swap(array, 0, arrayLength - 1 - i);
        }
        return array;
    }


    private static void swap(int[] data, int i, int j) {
        int tmp = data[i];
        data[i] = data[j];
        data[j] = tmp;
    }

    private static void buildMaxHeap(int[] data, int lastIndex) {
        for (int i = (lastIndex - 1) / 2; i >= 0; i--) {
            int k = i;
            while (k * 2 + 1 <= lastIndex) {
                int biggerIndex = 2 * k + 1;
                if (biggerIndex < lastIndex) {
                    if (data[biggerIndex] < data[biggerIndex + 1]) {
                        biggerIndex++;
                    }
                }

                if (data[k] < data[biggerIndex]) {
                    swap(data, k, biggerIndex);
                    k = biggerIndex;
                } else {
                    break;
                }
            }
        }
    }

运行

/**
     * 待排序的数组
     */
    private static int[] array = {
            12, 10, 5, 9, 5, 32, 16, 1, 9, 99, 80, 3, 18, 19, 20, 25, 7, 15
    };

    public static void main(String[] args) {

        int[] result = SortUtils.heapSort(array.clone());
        System.out.println(Arrays.toString(result));

    }

输出

[1, 3, 5, 5, 7, 9, 9, 10, 12, 15, 16, 18, 19, 20, 25, 32, 80, 99]