> For the complete documentation index, see [llms.txt](https://leetcodebook-1.gitbook.io/top-interview-150/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://leetcodebook-1.gitbook.io/top-interview-150/bfs/minimum-genetic-mutation.md).

# 最小基因变化

题目链接: <https://leetcode.cn/problems/minimum-genetic-mutation>

## 解题思路：

1. 判断`startGene`与`endGene`是否相等，相等直接返回0
2. 将`bank`转成`map`，判断`endGene`是否在`bank`中，不在直接返回-1
3. 从`startGene`开始处理，将每个字符用`ACGT`中与之不同的字符进行替换，并判断生成的新的基因是否在`bank`中，如果在，则判断是否是`endGene`，若是，则返回`step+1`，否则重新组建`step`存入队列，同时将该基因从`bank`中删除(若后续基因变换出现重复，那变换次数必然比这次多，所以可以直接从`bank`中移除不用判断是否重复)
4. 重复步骤3，直至找到`endGene`或者`queue`清空，若`queue`清空，则返回-1

```go
type step struct {
	value string
	step  int
}

func minMutation(startGene string, endGene string, bank []string) int {
	if startGene == endGene {
		return 0
	}
	bankMap := make(map[string]bool, len(bank))
	for _, item := range bank {
		bankMap[item] = true
	}
	if !bankMap[endGene] {
		return -1
	}
	queue := []step{{startGene, 0}}
	for len(queue) > 0 {
		item := queue[0]
		queue = queue[1:]
		for i, char := range item.value {
			for _, sig := range "ACGT" {
				if sig != char {
					next := item.value[:i] + string(sig) + item.value[i+1:]
					if bankMap[next] {
						if next == endGene {
							return item.step + 1
						}
						delete(bankMap, next)
						queue = append(queue, step{next, item.step + 1})
					}
				}
			}
		}
	}
	return -1
}
```

## 复杂度分析

* **时间复杂度：** 时间复杂度为$$O(c*n*m)$$,$$n$$为基因序列的长度，$$m$$为`bank`的长度，$$c$$为基因的字符个数`ACGT`
* **空间复杂度：** 空间复杂度为$$O(c*n*m)$$,$$n$$为基因序列的长度，$$m$$为`bank`的长度，$$c$$为基因的字符个数`ACGT`


---

# Agent Instructions
This documentation is published with GitBook. GitBook is the documentation platform designed so that both humans and AI agents can read, navigate, and reason over technical content effectively. Learn more at gitbook.com.

## Querying This Documentation
If you need additional information that is not directly available in this page, you can query the documentation by asking a question.

Perform an HTTP GET request on the following URL with the `ask` and `goal` query parameters:

```
GET https://leetcodebook-1.gitbook.io/top-interview-150/bfs/minimum-genetic-mutation.md?ask=<question>&goal=<user_goal>
```

`ask` is the immediate question: it should be specific, self-contained, and written in natural language.
`goal` is what the user is ultimately trying to achieve, the reason they need the answer. Sharing it helps GitBook give you a better, more relevant answer. A goal is most helpful when it describes the outcome the user wants rather than restating the question. For example, with `ask=how do I create an API token`, a goal like `automate deployments from our CI pipeline` lets GitBook tailor the answer to that use case.

The response will contain a direct answer to the question and relevant excerpts and sources from the documentation.

Use this mechanism when the answer is not explicitly present in the current page, you need clarification or additional context, or you want to retrieve related documentation sections.