17. 电话号码的字母组合

最新推荐文章于 2026-01-01 15:39:09 发布

原创最新推荐文章于 2026-01-01 15:39:09 发布 · 185 阅读

0 ·

CC 4.0 BY-SA版权

文章标签：

#java #leetcode #算法

leetcode-hot100 专栏收录该内容

96 篇文章

订阅专栏

https://leetcode.cn/problems/letter-combinations-of-a-phone-number/description/?envType=study-plan-v2&envId=top-interview-150

思路：题目要求我们穷举所有的字母情况，这显然很适合使用dfs+回溯解决

class Solution {
    String[][] str = {{"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"}};
    public List<String> letterCombinations(String digits) {
        List<String> ans = new ArrayList<>();
        if(digits.isEmpty()) return ans;
        dfs(ans, digits, 0, new StringBuilder());
        return ans;
    }

    public void dfs(List<String> ans, String digits, int index, StringBuilder currStr) {
        if(index == digits.length()) {
            ans.add(currStr.toString());
            return;
        }
        for(int i = 0; i < str[digits.charAt(index) - '2'].length; i++) {
            currStr.append(str[digits.charAt(index) - '2'][i]);
            dfs(ans, digits, index + 1, currStr);
            // 回溯其它情况
            currStr.deleteCharAt(currStr.length() - 1);
        }
    }

}