#17 Letter Combinations of a Phone Number有问题_letter combinations of a phone number 溢出问题-优快云博客

本文链接：https://blog.youkuaiyun.com/private_void/article/details/45892813

本文介绍了一种基于电话键盘输入数字生成所有可能的字母组合的算法实现。通过递归方式构建所有可能的字符串组合，并提供了详细的代码示例。

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题目：

Given a digit string, return all possible letter combinations that the number could represent.

A mapping of digit to letters (just like on the telephone buttons) is given below.

Input:Digit string "23"
Output: ["ad", "ae", "af", "bd", "be", "bf", "cd", "ce", "cf"].

Note:
Although the above answer is in lexicographical order, your answer could be in any order you want.

题解：

不太会，找了个代码，运行错误，先存着吧，以后看

public class Solution {
    public List<String> letterCombinations(String digits) {
        ArrayList<String> result=new ArrayList<String>();
        if(digits==null)return result;
        String[] keyboard={"","","abc","def","ghi","jkl","mno","pqrs","tuv","wxyz"};
        StringBuilder current=new StringBuilder();
        int index=0;
        buildResult(digits, index, current, keyboard, result);
        return result;
    }
    private void buildResult(String digits, int index, StringBuilder current, String[] keyboard, ArrayList<String> result){
        if (index==digits.length()){
            result.add(current.toString());
            return;
        }
        int  num=digits.charAt(index)-'0'; // get integer number 
        for(int i=0; i<keyboard[num].length(); i++){
            current.append(keyboard[num].charAt(i));
            buildResult(digits, index+1, current, keyboard, result);
            current.deleteCharAt(current.length()-1);
        }
     }
}