ARTS-WEEK2

#ARTS #Leetcode

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本周ARTS打卡内容：

Algorithm 来源 LeetCode17
Review 分享一篇go的内存管理
Tip 分享linux命令行查看java线程、内存情况
Share 分享golang Gin框架的实践

Algorithm

LeetCode的17题，手机的字母组合问题：
https://leetcode.com/problems/letter-combinations-of-a-phone-number/

题目要求，给出一个由2-9组成的字符串，返回数字字符串对应的所有可能的字母组合。数字到字母的映射可见手机。

Telephone

首先想到的解法是遍历，遍历数字字符串数组，把每次数字对应的字母列表轮询加到前一步得到的字母列表中，比如“23”，第一个数字对应[“a”,”b”,”c”]，第二个数字对应[“d”,”e”,”f”]，将第一个数组和第二个数组遍历组合得到[“ad”, “ae”, “af”, “bd”, “be”, “bf”, “cd”, “ce”, “cf”]，若后续还有数字，将其对应的字母列表与该列表继续遍历组合。代码如下：

func letterCombinations(digits string)  []string{
	var result, next []string
	for i := 0 ;i< len(digits); i++ {
		list := numToChar(string(digits[i]))
		for _ , l := range list {
			if result == nil {
				next = append(next, l)
			} else {
				for _, v := range result {
					next = append(next, v+l)
				}
			}
		}
		result = next
		next = nil
	}
	return result
}

func numToChar(k string) []string {
	if k == "0" {
		return []string{" "}
	}
	if k == "1" {
		return []string{""}
	}
	if k == "2" {
		return []string{"a","b","c"}
	}
	if k == "3" {
		return []string{"d","e","f"}
	}
	if k == "4" {
		return []string{"g","h","i"}
	}
	if k == "5" {
		return []string{"j","k","l"}
	}
	if k == "6" {
		return []string{"m","n","o"}
	}
	if k == "7" {
		return []string{"p","q","r","s"}
	}
	if k == "8" {
		return []string{"t","u","v"}
	}
	if k == "9" {
		return []string{"w","x","y","z"}
	}
	return nil
}