逆序对个数求解用python怎么实现
时间: 2023-05-22 14:03:14 浏览: 58
逆序对个数可以使用归并排序来实现,具体步骤如下:
1. 分治:将数组不断二分,直到每个部分中只有一个元素。
2. 合并:将部分合并排序并统计逆序对。
具体实现代码如下:
def merge_sort_count(nums):
def merge(left, right):
result = []
i, j, count = 0, 0, 0
while i < len(left) and j < len(right):
if left[i] <= right[j]:
result.append(left[i])
i += 1
else:
result.append(right[j])
j += 1
count += len(left) - i
result += left[i:]
result += right[j:]
return result, count
if len(nums) <= 1:
return nums, 0
mid = len(nums) // 2
left, count_left = merge_sort_count(nums[:mid])
right, count_right = merge_sort_count(nums[mid:])
result, count = merge(left, right)
count += count_left + count_right
return result, count
nums = [1, 3, 2, 4, 5]
result, count = merge_sort_count(nums)
print(count)
输出结果:1
注意:以上代码只是用来解决逆序对问题的,不一定适合完整的应用场景。