编写Array_Swap函数实现整数列表中对应位置元素的奇偶条件交换

Let's work through this problem to get the desired behavior. First, let's restate the requirements clearly to make sure we're on the same page:

Requirements #

• Define a function Array_Swap(List, Size) that takes an integer list and its length as parameters
• Swap elements symmetrically: first ↔ last, second ↔ second-last, etc.
• Only perform the swap if at least one of the two elements is odd
• Print the modified list after all valid swaps
• Example: Input list [5, 16, 4, 7, 19, 8, 2] should become [2, 16, 19, 7, 4, 8, 5]

Issues with the Original Code #

The provided code doesn't implement the swap logic correctly — it's just assigning values from the middle of the list to the front, and there's no check for odd elements. Let's fix that.

Corrected Code #

def Array_Swap(List, Size):
    # Iterate through the first half of the list
    for i in range(Size // 2):
        # Get the symmetric index from the end
        other_idx = Size - 1 - i
        # Check if at least one element is odd
        if List[i] % 2 != 0 or List[other_idx] % 2 != 0:
            # Perform the swap (Python's tuple unpacking makes this clean)
            List[i], List[other_idx] = List[other_idx], List[i]
    # Print the modified list
    print("交换后的列表:", List)

# Get user input
L = []
n = int(input("请输入元素个数: "))
for i in range(n):
    x = int(input(f"请输入第{i+1}个元素: "))
    L.append(x)

# Call the function
Array_Swap(L, len(L))

How It Works #

1. Loop Through Half the List: We only need to iterate up to Size//2 because swapping the first half with the second half covers all symmetric pairs.
2. Symmetric Index Calculation: For each index i, the corresponding pair is at Size - 1 - i (e.g., for a 7-element list, i=0 pairs with 6, i=1 pairs with 5, i=2 pairs with 3).
3. Odd Check: The condition List[i] % 2 !=0 or List[other_idx]%2 !=0 ensures we only swap if at least one element is odd.
4. Swap Operation: Python's tuple unpacking (a, b = b, a) is a concise way to swap two elements without needing a temporary variable.

Test the Example #

If we input the sample list [5,16,4,7,19,8,2]:

• i=0: 5 (odd) and 2 (even) → swap → list becomes [2,16,4,7,19,8,5]
• i=1:16 (even) and8 (even) → no swap
• i=2:4 (even) and19 (odd) → swap → list becomes [2,16,19,7,4,8,5]
• i=3: We stop here since 7//2=3, range(3) is 0,1,2.

Which matches the expected output perfectly!

内容的提问来源于stack exchange，提问作者recklessdude777