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面试题 16.20. T9键盘 ​

题目 ​

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：

示例 1:

输入: num = "8733", words = ["tree", "used"]
输出: ["tree", "used"]
输入: num = "8733", words = ["tree", "used"]
输出: ["tree", "used"]

示例 2:

输入: num = "2", words = ["a", "b", "c", "d"]
输出: ["a", "b", "c"]
输入: num = "2", words = ["a", "b", "c", "d"]
输出: ["a", "b", "c"]

提示：

  • num.length <= 1000
  • words.length <= 500
  • words[i].length == num.length
  • num中不会出现 0, 1 这两个数字

题解 ​

java
public List<String> getValidT9Words(String num, String[] words) {
    // 字典对应关系
    char[] dict = new char[]{
        '2', '2', '2',
        '3', '3', '3',
        '4', '4', '4',
        '5', '5', '5',
        '6', '6', '6',
        '7', '7', '7', '7',
        '8', '8', '8',
        '9', '9', '9', '9'
    };

    return
        Arrays.stream(words)
            .filter(word ->
                IntStream.range(0, word.length())
                    .allMatch(it -> num.charAt(it) == dict[word.charAt(it) - 'a'])
            )
            .collect(Collectors.toList());
}
public List<String> getValidT9Words(String num, String[] words) {
    // 字典对应关系
    char[] dict = new char[]{
        '2', '2', '2',
        '3', '3', '3',
        '4', '4', '4',
        '5', '5', '5',
        '6', '6', '6',
        '7', '7', '7', '7',
        '8', '8', '8',
        '9', '9', '9', '9'
    };

    return
        Arrays.stream(words)
            .filter(word ->
                IntStream.range(0, word.length())
                    .allMatch(it -> num.charAt(it) == dict[word.charAt(it) - 'a'])
            )
            .collect(Collectors.toList());
}