DFS做法， 能满足需求，有改进的地方欢迎大家提出 import java.util.*; //Author: Zhenjie Hao public class Main {     public static void main(String[] args){         int input = 123;         List<List<String>> result = new ArrayList<>();         result = converse(input);         display(result);              }     public static List<List<String>> converse(int input){         String str = String.valueOf(input);         List<List<String>> result = new ArrayList<>();         dfs(str, 0 , new ArrayList<>(), result);         return result;     }     public static void dfs(String str, int startIndex, List<String> path, List<List<String>> result){         if(startIndex == str.length()){             result.add(new ArrayList<String>(path));         }         for(int i = startIndex + 1; i <= str.length(); i++){             String sub = str.substring(startIndex, i);             if(!isValid(sub)){                 break;             }             path.add(numToAlg(sub));             dfs(str, i, path, result);             path.remove(path.size()-1);         }     }     public static boolean isValid(String str){         //str = "12" or "27"         if(str.charAt(0) == '0'){             return false;         }         int num = Integer.parseInt(str);         if(num < 1 || num > 26){             return false;         }         return true;     }     public static String numToAlg(String str){         //str = "12"         //putput = "d"         int num = Integer.parseInt(str);         return String.valueOf((char)('a' + num - 1));     }     public static void display(List<List<String>> result){         for(int i = 0; i < result.size(); i++){             StringBuilder sb = new StringBuilder();             for(int j = 0; j < result.get(i).size(); j++){                 sb.append(result.get(i).get(j));                              }             System.out.println(sb.toString());         }     } }