LeetCode刷题日志-17.电话号码的字母组合

index.php/tags-41973.html" >���暴力解法，digits有多长，就循环多少次进行字母组合

class Solution {    public List letterCombinations(String digits) {        List reslut = new ArrayList();        if(digits.equals(""))        return reslut;       Map letter_hash = new HashMap() {{            put(2, "abc");            put(3, "def");            put(4, "ghi");            put(5, "jkl");            put(6, "mno");            put(7, "pqrs");            put(8, "tuv");            put(9, "wxyz");        }};        if(digits.length() == 1){            for(char c : letter_hash.get(Integer.parseInt(String.valueOf(digits.charAt(0)))).toCharArray()){                reslut.add(String.valueOf(c));            }        }                if(digits.length() == 2){            for(char c : letter_hash.get(Integer.parseInt(String.valueOf(digits.charAt(0)))).toCharArray()){                StringBuilder re  =new StringBuilder();                for(char d : letter_hash.get(Integer.parseInt(String.valueOf(digits.charAt(1)))).toCharArray()){                    re.append(String.valueOf(c));                    re.append(String.valueOf(d));                    reslut.add(re.toString());                    re.delete(0,re.length());                }            }        }        if(digits.length() == 3){            for(char c : letter_hash.get(Integer.parseInt(String.valueOf(digits.charAt(0)))).toCharArray()){                StringBuilder re  =new StringBuilder();                for(char d : letter_hash.get(Integer.parseInt(String.valueOf(digits.charAt(1)))).toCharArray()){                    for(char e : letter_hash.get(Integer.parseInt(String.valueOf(digits.charAt(2)))).toCharArray()){                        re.append(String.valueOf(c));                        re.append(String.valueOf(d));                        re.append(String.valueOf(e));                        reslut.add(re.toString());                        re.delete(0,re.length());                    }                }            }        }        if(digits.length() == 4){            for(char c : letter_hash.get(Integer.parseInt(String.valueOf(digits.charAt(0)))).toCharArray()){                StringBuilder re  =new StringBuilder();                for(char d : letter_hash.get(Integer.parseInt(String.valueOf(digits.charAt(1)))).toCharArray()){                    for(char e : letter_hash.get(Integer.parseInt(String.valueOf(digits.charAt(2)))).toCharArray()){                        for(char f : letter_hash.get(Integer.parseInt(String.valueOf(digits.charAt(3)))).toCharArray()){                            re.append(String.valueOf(c));                            re.append(String.valueOf(d));                            re.append(String.valueOf(e));                            re.append(String.valueOf(f));                            reslut.add(re.toString());                            re.delete(0,re.length());                        }                    }                }            }        }    return reslut;    }}