t9-lcci

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英文版：Cracking the Coding Interview，源自硅谷程序员的面试红宝书

LCCI

On old cell phones, users typed on a numeric keypad and the phone would provide a list of words that matched these numbers. Each digit mapped to a set of 0&nbsp;- 4 letters. Implement an algo&shy;rithm to return a list of matching words, given a sequence of digits. You are provided a list of valid words. The mapping is shown in the diagram below:

<img src="https://assets.leetcode-cn.com/aliyun-lc-upload/original_images/17_telephone_keypad.png" style="width: 200px;" />

Example 1:

<pre>
Input: num = &quot;8733&quot;, words = [&quot;tree&quot;, &quot;used&quot;]
Output: [&quot;tree&quot;, &quot;used&quot;]
</pre>

Example 2:

<pre>
Input: num = &quot;2&quot;, words = [&quot;a&quot;, &quot;b&quot;, &quot;c&quot;, &quot;d&quot;]
Output: [&quot;a&quot;, &quot;b&quot;, &quot;c&quot;]</pre>

Note:

<ul>
	<li><code>num.length &lt;= 1000</code></li>
	<li><code>words.length &lt;= 500</code></li>
	<li><code>words[i].length == num.length</code></li>
	<li><code>There are no number 0 and 1 in num</code>.</li>
</ul>

getValidT9Words

T9 LCCI

Array

Hash Table

String

在老式手机上，用户通过数字键盘输入，手机将提供与这些数字相匹配的单词列表。每个数字映射到0至4个字母。给定一个数字序列，实现一个算法来返回匹配单词的列表。你会得到一张含有有效单词的列表。映射如下图所示：

<img src="https://assets.leetcode-cn.com/aliyun-lc-upload/original_images/17_telephone_keypad.png" style="width: 200px;" />

示例 1：

<pre>
输入：num = "8733", words = ["tree", "used"]
输出：["tree", "used"]
</pre>

示例 2：

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

提示：

<ul>
	<li><code>num.length &lt;= 1000</code></li>
	<li><code>words.length &lt;= 500</code></li>
	<li><code>words[i].length == num.length</code></li>
	<li><code>num</code>中不会出现 0, 1 这两个数字</li>
</ul>