LeetCode 017 Letter Combinations of a Phone Number

题目

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字符串按照zigzag排列，最后按照行输出结果。

代码

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 public static List<String> letterCombinations(String digits) {        List<String> ans = new ArrayList<String>();        if(digits == null || digits.length() == 0){            return ans;        }        String[] record = {"","","abc","def","ghi","jkl","mno","pqrs","tuv","wxyz"};        StringBuffer sb = new StringBuffer();        useme(ans,record,digits,0,sb);                return ans;    }        public static void useme(List<String> ans,     String[] record, String digits, int index,StringBuffer sb){        if(index == digits.length()){            ans.add(new String(sb));            return ;        }                        String curStr = record[digits.charAt(index)-'0'];        if(curStr.equals("")){        useme(ans,record,digits,index+1,sb);        }        for(int i =0;i<curStr.length();i++){            char curChar = curStr.charAt(i);            sb.append(curChar);            useme(ans,record,digits,index+1,sb);            sb.deleteCharAt(sb.length()-1);        }            }        

要注意 0,1 的时候，可能进入不了循环，所以要加一个判断，直接跳过他们。