gold-16-20

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"]

示例 2:

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

//leetcode submit region begin(Prohibit modification and deletion)
class Solution {
    public List<String> getValidT9Words(String num, String[] words) {
        char[][] charMap = {{'a', 'b', 'c'}, {'d', 'e', 'f'}, {'g', 'h', 'i'}, {'j', 'k', 'l'}, {'m', 'n', 'o'}, {'p', 'q', 'r', 's'}, {'t', 'u', 'v'}, {'w', 'x', 'y', 'z'}};
        List<String> result = new ArrayList<>();

        for (String word : words) {
            if (num.length() != word.length()) {
                continue;
            }

            boolean isValid = true;
            for (int i = 0; i < num.length(); i++) {
                char ch = word.charAt(i);
                char numCh = num.charAt(i);
                boolean isMatch = false;


                char[] charArr = charMap[numCh - '2'];
                for (char c : charArr) {
                    if (c == ch) {
                        isMatch = true;
                        break;
                    }
                }
                if (!isMatch) {
                    isValid = false;
                    break;
                }
            }

            if (isValid) {
                result.add(word);
            }
        }

        return result;
    }
}
//leetcode submit region end(Prohibit modification and deletion)