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Description
tab: English
<p>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 <strong>any order</strong>.</p>
<p>A mapping of digits to letters (just like on the telephone buttons) is given below. Note that 1 does not map to any letters.</p>
<img alt="" src="https://assets.leetcode.com/uploads/2022/03/15/1200px-telephone-keypad2svg.png" style="width: 300px; height: 243px;" />
<p> </p>
<p><strong class="example">Example 1:</strong></p>
<pre>
<strong>Input:</strong> digits = "23"
<strong>Output:</strong> ["ad","ae","af","bd","be","bf","cd","ce","cf"]
</pre>
<p><strong class="example">Example 2:</strong></p>
<pre>
<strong>Input:</strong> digits = "2"
<strong>Output:</strong> ["a","b","c"]
</pre>
<p> </p>
<p><strong>Constraints:</strong></p>
<ul>
<li><code>1 <= digits.length <= 4</code></li>
<li><code>digits[i]</code> is a digit in the range <code>['2', '9']</code>.</li>
</ul>
---
[submissions](https://leetcode.com/problems/letter-combinations-of-a-phone-number/submissions/) | [solutions](https://leetcode.com/problems/letter-combinations-of-a-phone-number/solutions/)
tab: 中文
<p>给定一个仅包含数字 <code>2-9</code> 的字符串，返回所有它能表示的字母组合。答案可以按 <strong>任意顺序</strong> 返回。</p>
<p>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。</p>
<p><img src="https://pic.leetcode.cn/1752723054-mfIHZs-image.png" style="width: 200px;" /></p>
<p> </p>
<p><strong>示例 1：</strong></p>
<pre>
<strong>输入：</strong>digits = "23"
<strong>输出：</strong>["ad","ae","af","bd","be","bf","cd","ce","cf"]
</pre>
<p><strong>示例 2：</strong></p>
<pre>
<strong>输入：</strong>digits = "2"
<strong>输出：</strong>["a","b","c"]
</pre>
<p> </p>
<p><strong>提示：</strong></p>
<ul>
<li><code>1 <= digits.length <= 4</code></li>
<li><code>digits[i]</code> 是范围 <code>['2', '9']</code> 的一个数字。</li>
</ul>
---
[提交记录](https://leetcode.cn/problems/letter-combinations-of-a-phone-number/submissions/) | [题解](https://leetcode.cn/problems/letter-combinations-of-a-phone-number/solution/)
Solutions & Notes
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