字符串全排列（Java版本自己用）

 我面试的时候写的版本（运行为空 存在Bug）

import java.util.Scanner;
import java.util.*;
public class Main {public static void main(String[] args) {String s="abc";char[] str=s.toCharArray();String[] ss=new String[str.length];for(int i=0;i<str.length;i++){ss[i]=String.valueOf(str[i]);}List<List<String>> result=new ArrayList<>();result=per(ss);System.out.println(result);}public static List<List<String>> per(String[] s){int len=s.length;List<List<String>> res=new ArrayList<>();if(len==0){return res;}boolean[] used=new boolean[len];List<String> path=new ArrayList<>();dfs(s,len,0,path,used,res);return res;}public static void dfs(String[] s,int len,int depth,List<String> path,boolean[] used,List<List<String>> res){if(depth==len){res.add(path);return;}for(int i=0;i<len;i++){if(!used[i]){path.add(s[i]);used[i]=true;dfs(s,len,depth+1,path,used,res);used[i]=false;path.remove(path.size()-1);}}}
}

修改后正确的：

import java.util.*;
public class Main {public static void main(String[] args) {String s="abc";char[] str=s.toCharArray();String[] ss=new String[str.length];for(int i=0;i<str.length;i++){ss[i]=String.valueOf(str[i]);}List<List<String>> result = new ArrayList<>();result = per(ss);System.out.println(result);}public static List<List<String>> per(String[] s){int len = s.length;List<List<String>> res = new ArrayList<>();if(len == 0){return res;}boolean[] used = new boolean[len];List<String> path = new ArrayList<>();dfs(s, len, 0, path, used, res);return res;}public static void dfs(String[] s, int len, int depth, List<String> path, boolean[] used, List<List<String>> res){if(depth == len){res.add(new ArrayList<>(path));return;}for(int i = 0; i < len; i++){if(!used[i]){path.add(s[i]);used[i] = true;dfs(s, len, depth + 1, path, used, res);used[i] = false;path.remove(path.size() - 1);}}}
}