java字符串字符排列组合_如何在Java中查找字符串的所有排列

秒速五厘米 2023-02-28 06:14 34阅读 0赞

java字符串字符排列组合

In this tutorial, we will learn how to find the permutation of a String in a Java Program. It’s a tricky question and asked mostly in Java interviews.

在本教程中，我们将学习如何在Java程序中查找字符串的排列。 这是一个棘手的问题，主要在Java访谈中提出。

## Java中字符串置换的算法 **(****Algorithm for Permutation of a String in Java****)** ##

We will first take the first character from the String and permute with the remaining chars.

我们将首先从String中获取第一个字符，并用剩余的字符进行置换。

If String = “ABC”

如果String =“ ABC”

First char = A and remaining chars permutations are BC and CB.

第一个字符= A，剩余的字符排列为BC和CB。

Now we can insert first char in the available positions in the permutations.

现在，我们可以在排列的可用位置插入第一个字符。

BC -> ABC, BAC, BCA

卑诗省-> ABC，BAC，BCA

CB -> ACB, CAB, CBA

CB-> ACB，CAB，CBA

We can write a recursive function to return the permutations and then another function to insert the first characters to get the complete list of permutations.

我们可以编写一个递归函数以返回排列，然后编写另一个函数以插入第一个字符以获取排列的完整列表。

## Java程序打印字符串的排列 **(****Java Program to Print Permutations of a String****)** ##

package com.journaldev.java.string;
    
    import java.util.HashSet;
    import java.util.Set;
    
    /**
     * Java Program to find all permutations of a String
     * @author Pankaj
     *
     */
    public class StringFindAllPermutations {
        public static Set<String> permutationFinder(String str) {
            Set<String> perm = new HashSet<String>();
            //Handling error scenarios
            if (str == null) {
                return null;
            } else if (str.length() == 0) {
                perm.add("");
                return perm;
            }
            char initial = str.charAt(0); // first character
            String rem = str.substring(1); // Full string without first character
            Set<String> words = permutationFinder(rem);
            for (String strNew : words) {
                for (int i = 0;i<=strNew.length();i++){
                    perm.add(charInsert(strNew, initial, i));
                }
            }
            return perm;
        }
    
        public static String charInsert(String str, char c, int j) {
            String begin = str.substring(0, j);
            String end = str.substring(j);
            return begin + c + end;
        }
    
        public static void main(String[] args) {
            String s = "AAC";
            String s1 = "ABC";
            String s2 = "ABCD";
            System.out.println("\nPermutations for " + s + " are: \n" + permutationFinder(s));
            System.out.println("\nPermutations for " + s1 + " are: \n" + permutationFinder(s1));
            System.out.println("\nPermutations for " + s2 + " are: \n" + permutationFinder(s2));
        }
    }

I have used [Set][] to store the string permutations. So that duplicates are removed automatically.

我用[Set][]来存储字符串排列。 这样可以自动删除重复项。

## 输出量 **(****Output****)** ##

Permutations for AAC are: 
    [AAC, ACA, CAA]
    
    Permutations for ABC are: 
    [ACB, ABC, BCA, CBA, CAB, BAC]
    
    Permutations for ABCD are: 
    [DABC, CADB, BCAD, DBAC, BACD, ABCD, ABDC, DCBA, ADBC, ADCB, CBDA, CBAD, DACB, ACBD, CDBA, CDAB, DCAB, ACDB, DBCA, BDAC, CABD, BADC, BCDA, BDCA]

That’s all for finding all permutations of a String in Java.

这就是查找Java中String的所有排列的全部。

[GitHub Repository][]. [GitHub Repository][]下载示例程序代码。

> 翻译自: [https://www.journaldev.com/526/permutation-of-string-in-java][https_www.journaldev.com_526_permutation-of-string-in-java]

java字符串字符排列组合

[Set]: https://www.journaldev.com/13242/java-set
[GitHub Repository]: https://github.com/journaldev/journaldev/blob/master/CoreJavaProjects/String-Programs/src/main/java/com/journaldev/java/string/StringFindAllPermutations.java
[https_www.journaldev.com_526_permutation-of-string-in-java]: https://www.journaldev.com/526/permutation-of-string-in-java