【急求】给定数的序列只能相邻的两个数两两交换，最少需要多少次交换成为一个排列的序列，只需写出交换次

Posted 2023-03-25

Give you a sequence of N numbers. The goal is to move the numbers around so that at the end the sequence is ordered. The only operation allowed is to swap two adjacent numbers. Let us try an example:
Start with: 1 4 3 2
swap (1 4) 4 1 3 2
swap (3 2) 4 1 2 3
swap (1 2) 4 2 1 3
swap (4 2) 2 4 1 3
swap (1 4) 2 1 4 3
swap (4 3) 2 1 3 4
swap (2 1) 1 2 3 4
So the sequence (1 4 3 2) can be sorted with seven swaps of adjacent numbers. However, it is even possible to sort it with such swaps:
Start with: 1 4 3 2
swap (4 3) 1 3 4 2
swap (4 2) 1 3 2 4
swap (3 2) 1 2 3 4
The question is: What is the minimum number of swaps of adjacent numbers to sort a given sequence?
我的作业已经做完了，ACCEPT了，但是我不理解我在用归并排序的时候，总是RUNTIME ERROR 同学说应该是realloc的时候出了问题，谁能给个具体解释

参考技术A 应该是3步吧
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