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135 lines
3.9 KiB
Markdown
135 lines
3.9 KiB
Markdown
# [1694. Reformat Phone Number](https://leetcode.com/problems/reformat-phone-number/)
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## 题目
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You are given a phone number as a string `number`. `number` consists of digits, spaces `' '`, and/or dashes `'-'`.
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You would like to reformat the phone number in a certain manner. Firstly, **remove** all spaces and dashes. Then, **group** the digits from left to right into blocks of length 3 **until** there are 4 or fewer digits. The final digits are then grouped as follows:
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- 2 digits: A single block of length 2.
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- 3 digits: A single block of length 3.
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- 4 digits: Two blocks of length 2 each.
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The blocks are then joined by dashes. Notice that the reformatting process should **never** produce any blocks of length 1 and produce **at most** two blocks of length 2.
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Return *the phone number after formatting.*
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**Example 1:**
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```
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Input: number = "1-23-45 6"
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Output: "123-456"
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Explanation: The digits are "123456".
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Step 1: There are more than 4 digits, so group the next 3 digits. The 1st block is "123".
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Step 2: There are 3 digits remaining, so put them in a single block of length 3. The 2nd block is "456".
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Joining the blocks gives "123-456".
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```
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**Example 2:**
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```
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Input: number = "123 4-567"
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Output: "123-45-67"
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Explanation: The digits are "1234567".
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Step 1: There are more than 4 digits, so group the next 3 digits. The 1st block is "123".
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Step 2: There are 4 digits left, so split them into two blocks of length 2. The blocks are "45" and "67".
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Joining the blocks gives "123-45-67".
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```
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**Example 3:**
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```
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Input: number = "123 4-5678"
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Output: "123-456-78"
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Explanation: The digits are "12345678".
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Step 1: The 1st block is "123".
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Step 2: The 2nd block is "456".
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Step 3: There are 2 digits left, so put them in a single block of length 2. The 3rd block is "78".
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Joining the blocks gives "123-456-78".
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```
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**Example 4:**
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```
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Input: number = "12"
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Output: "12"
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```
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**Example 5:**
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```
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Input: number = "--17-5 229 35-39475 "
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Output: "175-229-353-94-75"
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```
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**Constraints:**
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- `2 <= number.length <= 100`
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- `number` consists of digits and the characters `'-'` and `' '`.
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- There are at least **two** digits in `number`.
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## 题目大意
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给你一个字符串形式的电话号码 number 。number 由数字、空格 ' '、和破折号 '-' 组成。
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请你按下述方式重新格式化电话号码。
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- 首先，删除 所有的空格和破折号。
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- 其次，将数组从左到右 每 3 个一组 分块，直到 剩下 4 个或更少数字。剩下的数字将按下述规定再分块：
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- 2 个数字：单个含 2 个数字的块。
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- 3 个数字：单个含 3 个数字的块。
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- 4 个数字：两个分别含 2 个数字的块。
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最后用破折号将这些块连接起来。注意，重新格式化过程中 不应该 生成仅含 1 个数字的块，并且 最多 生成两个含 2 个数字的块。返回格式化后的电话号码。
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## 解题思路
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- 简单题。先判断号码是不是 2 位和 4 位，如果是，单独输出这 2 种情况。剩下的都是 3 位以上了，取余，判断剩余的数字是 2 个还是 4 个。这时不可能存在剩 1 位数的情况。除 3 余 1，即剩 4 位的情况，末尾 4 位需要 2 个一组输出。除 3 余 2，即剩 2 位的情况。处理好末尾，再逆序每 3 个一组连接 "-" 即可。可能需要注意的 case 见 test 文件。
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## 代码
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```go
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package leetcode
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import (
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"strings"
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)
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func reformatNumber(number string) string {
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parts, nums := []string{}, []rune{}
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for _, r := range number {
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if r != '-' && r != ' ' {
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nums = append(nums, r)
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}
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}
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threeDigits, twoDigits := len(nums)/3, 0
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switch len(nums) % 3 {
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case 1:
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threeDigits--
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twoDigits = 2
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case 2:
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twoDigits = 1
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default:
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twoDigits = 0
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}
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for i := 0; i < threeDigits; i++ {
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s := ""
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s += string(nums[0:3])
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nums = nums[3:]
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parts = append(parts, s)
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}
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for i := 0; i < twoDigits; i++ {
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s := ""
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s += string(nums[0:2])
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nums = nums[2:]
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parts = append(parts, s)
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}
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return strings.Join(parts, "-")
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}
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``` |