使用ArrayList打印字符串的所有排列

给定一个字符串str ，任务是打印str的所有排列。
就排列的顺序而言，排列是一组对象的全部或一部分的排列。
例如，单词“ bat”和“ tab”代表相似的三个字母单词的两个不同的排列(或排列)。

例子：

Input: str = “abc”
Output: abc acb bac bca cba cab

Input: str = “bat”
Output: bat bta abt atb tba tab

方法：编写一个递归函数，该函数将生成字符串的所有排列。终止条件为传递的字符串为空时，在这种情况下，该函数将返回一个空的ArrayList。

下面是上述方法的实现：

Java

// Java implementation of the approach
import java.util.ArrayList;
  
public class GFG {
  
    // Utility function to print the contents
    // of the ArrayList
    static void printArrayList(ArrayList arrL)
    {
        arrL.remove("");
        for (int i = 0; i < arrL.size(); i++)
            System.out.print(arrL.get(i) + " ");
    }
  
    // Function to returns the arraylist which contains
    // all the permutation of str
    public static ArrayList getPermutation(String str)
    {
  
        // If string is empty
        if (str.length() == 0) {
  
            // Return an empty arraylist
            ArrayList empty = new ArrayList<>();
            empty.add("");
            return empty;
        }
  
        // Take first character of str
        char ch = str.charAt(0);
  
        // Take sub-string starting from the
        // second character
        String subStr = str.substring(1);
  
        // Recurvise call
        ArrayList prevResult = getPermutation(subStr);
  
        // Store the generated permutations
        // into the resultant arraylist
        ArrayList Res = new ArrayList<>();
  
        for (String val : prevResult) {
            for (int i = 0; i <= val.length(); i++) {
                Res.add(val.substring(0, i) + ch + val.substring(i));
            }
        }
  
        // Return the resultant arraylist
        return Res;
    }
  
    // Driver code
    public static void main(String[] args)
    {
        String str = "abc";
        printArrayList(getPermutation(str));
    }
}

C#

// C# implementation of the approach 
using System.Collections.Generic;
using System;
  
class GFG 
{ 
  
    // Utility function to print the contents 
    // of the ArrayList 
    static void printArrayList(List arrL) 
    { 
        arrL.Remove(""); 
        for (int i = 0; i < arrL.Count; i++) 
            Console.Write(arrL[i] + " "); 
    } 
  
    // Function to returns the arraylist which contains 
    // all the permutation of str 
    public static List getPermutation(String str) 
    { 
  
        // If string is empty 
        if (str.Length == 0)
        { 
  
            // Return an empty arraylist 
            List empty = new List(); 
            empty.Add(""); 
            return empty; 
        } 
  
        // Take first character of str 
        char ch = str[0]; 
  
        // Take sub-string starting from the 
        // second character 
        String subStr = str.Substring(1); 
  
        // Recurvise call 
        List prevResult = getPermutation(subStr); 
  
        // Store the generated permutations 
        // into the resultant arraylist 
        List Res = new List(); 
  
        foreach (String val in prevResult)
        { 
            for (int i = 0; i <= val.Length; i++) 
            { 
                Res.Add(val.Substring(0, i) + ch + val.Substring(i)); 
            } 
        } 
  
        // Return the resultant arraylist 
        return Res; 
    } 
  
    // Driver code 
    public static void Main(String[] args) 
    { 
        String str = "abc"; 
        printArrayList(getPermutation(str)); 
    } 
} 
  
// This code has been contributed by 29AjayKumar

输出：

abc bac bca acb cab cba