letter-combinations-of-a-phone-number

java

python

python3

mysql

mssql

oraclesql

csharp

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racket

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cangjie

Algorithms

Given a string containing digits from <code>2-9</code> inclusive, return all possible letter combinations that the number could represent. Return the answer in any order.

A mapping of digits to letters (just like on the telephone buttons) is given below. Note that 1 does not map to any letters.
<img alt="" src="https://assets.leetcode.com/uploads/2022/03/15/1200px-telephone-keypad2svg.png" style="width: 300px; height: 243px;" />
&nbsp;
Example 1:

<pre>
Input: digits = &quot;23&quot;
Output: [&quot;ad&quot;,&quot;ae&quot;,&quot;af&quot;,&quot;bd&quot;,&quot;be&quot;,&quot;bf&quot;,&quot;cd&quot;,&quot;ce&quot;,&quot;cf&quot;]
</pre>

Example 2:

<pre>
Input: digits = &quot;&quot;
Output: []
</pre>

Example 3:

<pre>
Input: digits = &quot;2&quot;
Output: [&quot;a&quot;,&quot;b&quot;,&quot;c&quot;]
</pre>

&nbsp;
Constraints:

<ul>
	<li><code>0 &lt;= digits.length &lt;= 4</code></li>
	<li><code>digits[i]</code> is a digit in the range <code>[&#39;2&#39;, &#39;9&#39;]</code>.</li>
</ul>

letterCombinations

Letter Combinations of a Phone Number

Generate Parentheses

generate-parentheses

括号生成

Combination Sum

combination-sum

组合总和

Binary Watch

binary-watch

二进制手表

Count Number of Texts

count-number-of-texts

统计打字方案数

Minimum Number of Pushes to Type Word I

minimum-number-of-pushes-to-type-word-i

输入单词需要的最少按键次数 I

Minimum Number of Pushes to Type Word II

minimum-number-of-pushes-to-type-word-ii

输入单词需要的最少按键次数 II

Hash Table

String

Backtracking

给定一个仅包含数字&nbsp;<code>2-9</code>&nbsp;的字符串，返回所有它能表示的字母组合。答案可以按 任意顺序 返回。

给出数字到字母的映射如下（与电话按键相同）。注意 1 不对应任何字母。

<img src="https://assets.leetcode-cn.com/aliyun-lc-upload/uploads/2021/11/09/200px-telephone-keypad2svg.png" style="width: 200px;" />

&nbsp;

示例 1：

<pre>
输入：digits = "23"
输出：["ad","ae","af","bd","be","bf","cd","ce","cf"]
</pre>

示例 2：

<pre>
输入：digits = ""
输出：[]
</pre>

示例 3：

<pre>
输入：digits = "2"
输出：["a","b","c"]
</pre>

&nbsp;

提示：

<ul>
	<li><code>0 &lt;= digits.length &lt;= 4</code></li>
	<li><code>digits[i]</code> 是范围 <code>['2', '9']</code> 的一个数字。</li>
</ul>