Question

我们使用Merge sort中的merge函数为2个数组（G和H）进行联接。数组是：

G = [3,5,8,9] , H = [1,2,5,7]

为了更好地理解，我还将添加合并功能代码：（来源：https://www.geeksforgeeks.org/python-program-for-merge-sort/）

def merge(arr, l, m, r): 
    n1 = m - l + 1
    n2 = r- m 

    # create temp arrays 
    L = [0] * (n1) 
    R = [0] * (n2) 

    # Copy data to temp arrays L[] and R[] 
    for i in range(0 , n1): 
        L[i] = arr[l + i] 

    for j in range(0 , n2): 
        R[j] = arr[m + 1 + j] 

    # Merge the temp arrays back into arr[l..r] 
    i = 0     # Initial index of first subarray 
    j = 0     # Initial index of second subarray 
    k = l     # Initial index of merged subarray 

    while i < n1 and j < n2 : 
        if L[i] <= R[j]: 
            arr[k] = L[i] 
            i += 1
        else: 
            arr[k] = R[j] 
            j += 1
        k += 1

    # Copy the remaining elements of L[], if there 
    # are any 
    while i < n1: 
        arr[k] = L[i] 
        i += 1
        k += 1

    # Copy the remaining elements of R[], if there 
    # are any 
    while j < n2: 
        arr[k] = R[j] 
        j += 1
        k += 1

这是我的思考过程：

Compare 1: 3 VS 1 [1]
Compare 2: 3 VS 2 [1,2]
Compare 3: 3 VS 5 [1,2,3]
Compare 4: 5 VS 5 [1,2,3,5]
Compare 5: 8 VS 5 [1,2,3,5,5]
Compare 6: 8 VS 7 [1,2,3,5,5,7]

当循环结束时，我们将元素从第一个数组复制到最终数组。因此，总的来说，我们有6个比较。但是，我的大学提供的答案是5，真的不知道为什么！

编辑： 当数组元素相等时，我们将它们都添加到新数组中并增加指向当前位置的变量。需要将类似以下内容添加到代码中：

if L[i] == R[j]:
    arr[k] = L[i]
    k += 1 
    arr[k] = R[j]
    i += 1
    j += 1

合并排序中元素比较的数量

0 个答案: