poj1804 Brainman 归并排序求逆序对

最新推荐文章于 2021-08-06 12:15:26 发布

ronwhite

最新推荐文章于 2021-08-06 12:15:26 发布

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文章标签：归并排序

本文链接：https://blog.youkuaiyun.com/qq_35644289/article/details/52970730

该博客介绍了一个使用归并排序算法求解逆序对的问题，通过分治思想，将序列分解并有序合并，当后区间最小值小于前区间最小值时，计数逆序对。给出的样例展示了不同输入情况下所需的最小交换次数。

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Problem
Here’s what Charlie thinks of. Imagine you get 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: 2 8 0 3
swap (2 8) 8 2 0 3
swap (2 0) 8 0 2 3
swap (2 3) 8 0 3 2
swap (8 0) 0 8 3 2
swap (8 3) 0 3 8 2
swap (8 2) 0 3 2 8
swap (3 2) 0 2 3 8
swap (3 8) 0 2 8 3
swap (8 3) 0 2 3 8

So the sequence (2 8 0 3) can be sorted with nine swaps of adjacent numbers. However, it is even possible to sort it with three such swaps:
Start with: 2 8 0 3
swap (8 0) 2 0 8 3
swap (2 0) 0 2 8 3
swap (8 3) 0 2 3 8

The question is: What is the minimum number of swaps of adjacent numbers to sort a given sequence?Since Charlie does not have Raymond’s mental capabilities, he decides to cheat. Here is where you come into play. He asks you to write a computer prog