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 scenariosif (str == null) {return null;} else if (str.length() == 0) {perm.add("");return perm;}char initial = str.charAt(0); // first characterString rem = str.substring(1); // Full string without first characterSet<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。

翻译自: https://www.journaldev.com/526/permutation-of-string-in-java

java字符串字符排列组合