常用排序算法之归并排序

归并排序算法

/**
     * 归并排序
     * @param array
     * @return
     */
    public static int[] mergingSort(int[] array) {
        sort(array, 0, array.length - 1);
        return array;
    }

    public static void sort(int[] data, int left, int right) {
        if (left < right) {
            //找出中间索引
            int center = (left + right) / 2;
            //对左边数组进行递归
            sort(data, left, center);
            //对右边数组进行递归
            sort(data, center + 1, right);
            merge(data, left, center, right);
        }
    }


    public static void merge(int[] data, int left, int center, int right) {
        int[] tmpArr = new int[data.length];
        int mid = center + 1;
        int third = left;
        int tmp = left;
        while (left <= center && mid <= right) {
            if (data[left] <= data[mid]) {
                tmpArr[third++] = data[left++];
            } else {
                tmpArr[third++] = data[mid++];
            }
        }
        while (mid <= right) {
            tmpArr[third++] = data[mid++];
        }
        while (left <= center) {
            tmpArr[third++] = data[left++];
        }
        while (tmp <= right) {
            data[tmp] = tmpArr[tmp++];
        }
    }

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.mergingSort(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]