通过代码实现计算由n个数组成的序列(整型数组a)的逆序数,并返回逆序数值。
时间: 2024-04-08 14:29:31 浏览: 70
一维数组元素引用的程序实例-谭浩强C语言第四版
以下是一个可以计算逆序数的示例代码:
```python
def merge_sort_count(arr):
if len(arr) <= 1:
return arr, 0
mid = len(arr) // 2
left, inv_count_left = merge_sort_count(arr[:mid])
right, inv_count_right = merge_sort_count(arr[mid:])
merged, inv_count_merge = merge_count(left, right)
return merged, inv_count_left + inv_count_right + inv_count_merge
def merge_count(left, right):
merged = []
inv_count = 0
i = j = 0
while i < len(left) and j < len(right):
if left[i] <= right[j]:
merged.append(left[i])
i += 1
else:
merged.append(right[j])
inv_count += len(left) - i
j += 1
merged.extend(left[i:])
merged.extend(right[j:])
return merged, inv_count
def calculate_inverse_count(arr):
_, inv_count = merge_sort_count(arr)
return inv_count
# 示例用法
arr = [4, 3, 2, 1]
inverse_count = calculate_inverse_count(arr)
print(f"Inverse count: {inverse_count}")
```
这段代码使用归并排序的思想来计算逆序数。它将数组不断分割为更小的子数组,然后再将这些子数组合并时计算逆序数。最终返回逆序数的值。
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