1. package com.model.recursion;
   
   import org.omg.PortableServer.LIFESPAN_POLICY_ID;
   
   import java.util.ArrayList;
   import java.util.List;
   
   /**
    * @Description:测试类
    * @Author: 张紫韩
    * @Crete 2021/8/29 21:52
    * 动态规划查找到一个字符串的所有子串
    */
   public class RecursionDemo01 {
   
       public static void main(String[] args) {
           String str="abc";
           ArrayList<String> resList = new ArrayList<>();
           getAllStr(str, 0, "",resList);
           for (String string:resList){
               System.out.println(string);
           }
   
       }
       public static void getAllStr(String str,int index,String path,List<String> resList){
           if (index==str.length()){
               resList.add(path);
               return;
           }
           getAllStr(str, index+1, path+str.charAt(index),resList);
           getAllStr(str, index+1, path,resList);
   
       }
   }

打印出一个字符串的全排列：

1. package com.model.recursion;
   
   import java.util.ArrayList;
   import java.util.List;
   
   /**
    * @Description:测试类
    * @Author: 张紫韩
    * @Crete 2021/8/29 22:29
    * 打印一个字符串的全排列
    */
   public class RecursionDemo02 {
       public static void main(String[] args) {
           char[] array="abc".toCharArray();
           swap(array, 0, 2);
   //        System.out.println(array);
           ArrayList<String> list = new ArrayList<>();
           arrangement(array, 0,list);
           for (String str:list){
               System.out.println(str);
           }
       }
       public static void arrangement(char[] array, int index, List<String> resList){
           if (index==array.length){
               resList.add(new String(array));
               return;
           }
           for (int i = index; i <array.length; i++) {
               swap(array, index, i);
               arrangement(array, index+1,resList);
               swap(array, i,index);
           }
   
       }
       public static void swap(char[] array,int left,int right){
           char l = array[left];
           char r = array[right];
           array[left]=r;
           array[right]=l;
       }
   }

2.  

   package com.model.recursion;
   
   import java.util.ArrayList;
   import java.util.List;
   
   /**
    * @Description:测试类
    * @Author: 张紫韩
    * @Crete 2021/8/29 22:29
    * 打印一个字符串的全排列，要求无重复的
    */
   public class RecursionDemo03 {
       public static void main(String[] args) {
           char[] array="abca".toCharArray();
   //        swap(array, 0, 2);
   ////        System.out.println(array);
           ArrayList<String> list = new ArrayList<>();
           arrangement(array, 0,list);
           for (String str:list){
               System.out.println(str);
           }
       }
       public static void arrangement(char[] array, int index, List<String> resList){
           if (index==array.length){
               resList.add(new String(array));
               return;
           }
   
           boolean[] arr = new boolean[26];
           for (int i = index; i <array.length; i++) {
               if (!arr[array[i]-'a']) {
                   arr[array[i]-'a']=true;
                   swap(array, index, i);
                   arrangement(array, index + 1, resList);
                   swap(array, index, i);
               }
           }
   
       }
       public static void swap(char[] array,int left,int right){
           char l = array[left];
           char r = array[right];
           array[left]=r;
           array[right]=l;
       }
   }

    

    

3.