leetcode-problemset/leetcode-cn/problem (English)/T9键盘(English) [t9-lcci].html

<p>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:</p>

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

<p><strong>Example 1:</strong></p>

<pre>
<strong>Input:</strong> num = &quot;8733&quot;, words = [&quot;tree&quot;, &quot;used&quot;]
<strong>Output:</strong> [&quot;tree&quot;, &quot;used&quot;]
</pre>

<p><strong>Example 2:</strong></p>

<pre>
<strong>Input:</strong> num = &quot;2&quot;, words = [&quot;a&quot;, &quot;b&quot;, &quot;c&quot;, &quot;d&quot;]
<strong>Output:</strong> [&quot;a&quot;, &quot;b&quot;, &quot;c&quot;]</pre>

<p>Note:</p>

<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>