面试题精选（84）：使序列有序的最少交换次数（minimum swaps） + 删除序列中所有重复的元素

最新推荐文章于 2025-05-29 08:22:48 发布

yysdsyl

最新推荐文章于 2025-05-29 08:22:48 发布

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文章标签：面试 duplicates delete algorithm system numbers

本文链接：https://blog.youkuaiyun.com/yysdsyl/article/details/4311031

该博客介绍了两个算法问题：一是求解使序列有序的最少交换次数，通过分析序列中的循环并进行适当交换达到排序；二是删除序列中所有重复的元素，通过标记法在常量空间和线性时间内完成。提供了C++实现代码。

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题目描述：（minimum swaps）

Given a sequence, we have to find the minimum no of swaps required to sort the sequence.

分析：

formula： no. of elements out of place - "cycles" in the sequence

A cycle is a set of elements, each of which is in the place of another. So in example sequences { 2, 1, 4, 3}, there are two cycles: {1, 2} and {3, 4}. 1 is in the place where 2 needs to go, and 2 is in the place where 1 needs to go 1, so they are a cycle; likewise with 3 and 4.

The sequences {3, 2, 1, 5, 6, 8, 4, 7 }also has two cycles: 3 is in the place of 1 which is in the place of 3, so {1, 3} is a cycle; 2 is in its proper place; and 4 is in the place of 7 which is in the place of 8 in place of 6 in place of 5 in place of 4, so {4, 7, 8, 6, 5} is a cycle. There are seven elements out of place in two cycles, so five swaps are needed.

实现：

e.g. { 2, 3, 1, 5, 6, 4}