JZ-027-字符串的排列 JZ-027-字符串的排列

字符串的排列题目描述

输入一个字符串,按字典序打印出该字符串中字符的所有排列。例如输入字符串abc，则按字典序打印出由字符a,b,c所能排列出来的所有字符串abc,acb,bac,bca,cab和cba。
【JZ-027-字符串的排列】题目链接: 字符串的排列

代码

import java.util.ArrayList; import java.util.Arrays; /** * 标题：字符串的排列 * 题目描述 * 输入一个字符串,按字典序打印出该字符串中字符的所有排列。例如输入字符串abc, * 则按字典序打印出由字符a,b,c所能排列出来的所有字符串abc,acb,bac,bca,cab和cba。 * 题目链接： * https://www.nowcoder.com/practice/fe6b651b66ae47d7acce78ffdd9a96c7?tpId=13&&tqId=11180&rp=1&ru=/ta/coding-interviews&qru=/ta/coding-interviews/question-ranking */ public class Jz27 { private ArrayList ret = new ArrayList<>(); public ArrayList permutation(String str) { if (str.length() == 0) { return ret; } char[] chars = str.toCharArray(); Arrays.sort(chars); backtracking(chars, new boolean[chars.length], new StringBuilder()); return ret; }private void backtracking(char[] chars, boolean[] hasUsed, StringBuilder s) { if (s.length() == chars.length) { ret.add(s.toString()); return; } for (int i = 0; i < chars.length; i++) { if (hasUsed[i]) { continue; } // 保证不重复 if (i != 0 && chars[i] == chars[i - 1] && hasUsed[i - 1]) { continue; } hasUsed[i] = true; s.append(chars[i]); backtracking(chars, hasUsed, s); s.deleteCharAt(s.length() - 1); hasUsed[i] = false; } }public static void main(String[] args) { Jz27 jz27 = new Jz27(); ArrayList result = jz27.permutation("abcdee"); System.out.println("size: " + result.size()); for (int i = 0; i < result.size(); i++) { System.out.println(result.get(i)); } } }