本文共 2119 字，大约阅读时间需要 7 分钟。
给定一个仅包含数字 2-9 的字符串，返回所有它能表示的字母组合。
给出数字到字母的映射如下（与电话按键相同）。注意 1 不对应任何字母。 输入："23" 输出：["ad", "ae", "af", "bd", "be", "bf", "cd", "ce", "cf"].
public class day { public static ArrayList twoFor(String x,ArrayList first_List) { int count = 0; ArrayList end_List = new ArrayList<>(); for(int j=0;j onefor(String x,ArrayList Beginning_list){ int count = 0; for(int j=0;j first_List,String input) { String x2 = "abc"; String x3 = "def"; String x4 = "ghi"; String x5 = "jkl"; String x6 = "mno"; String x7 = "pqrs"; String x8 = "tuv"; String x9 = "wxyz"; ArrayList end_List = new ArrayList<>(); if(input.charAt(0)=='2') { if(first_List.size()==0) { end_List=onefor(x2,first_List); }else { end_List = twoFor(x2, first_List); } }else if(input.charAt(0)=='3') { if(first_List.size()==0) { end_List=onefor(x3,first_List); }else { end_List = twoFor(x3, first_List); } }else if(input.charAt(0)=='4') { if(first_List.size()==0) { end_List=onefor(x4,first_List); }else { end_List = twoFor(x4, first_List); } }else if(input.charAt(0)=='5') { if(first_List.size()==0) { end_List=onefor(x5,first_List); }else { end_List = twoFor(x5, first_List); } }else if(input.charAt(0)=='6') { if(first_List.size()==0) { end_List=onefor(x6,first_List); }else { end_List = twoFor(x6, first_List); } }else if(input.charAt(0)=='7') { if(first_List.size()==0) { end_List=onefor(x7,first_List); }else { end_List = twoFor(x7, first_List); } }else if(input.charAt(0)=='8') { if(first_List.size()==0) { end_List=onefor(x8,first_List); }else { end_List = twoFor(x8, first_List); } }else{ if(first_List.size()==0) { end_List=onefor(x9,first_List); }else { end_List = twoFor(x9, first_List); } } String end_string = input.substring(1); if(end_string.equals("")) { System.out.println(end_List.size()); for(String end:end_List) { System.out.print(end+" "); } }else { phone_number(end_List,end_string); } } public static void main(String[] args) { int input = 2479; String input_string = String.valueOf(input); ArrayList loop = new ArrayList<>(); phone_number(loop,input_string); }}
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