题解 | #字符串的排列#

import java.util.*;

class Solution {
    StringBuffer sf = new StringBuffer();
    Set<String> set = new HashSet<>();
    public ArrayList<String> Permutation(String str) {
        ArrayList<String> alist = new ArrayList<>();
        Permutate(str.toCharArray());
        for(String s:set){
            alist.add(s);
        }
        return alist;

    }
    public void Permutate(char[] c){
        if(c.length<=1){
            sf.append(c[0]);
            set.add(sf.toString());
            sf.delete(sf.length()-1,sf.length());
            return;
        }
        for(int i=0;i<c.length;i++){
            sf.append(c[i]);
            char num[] = new char[c.length-1];
            int index = 0;
            for(int j=0;j<c.length;j++){
                if(j==i)continue;
                num[index++] = c[j];
            }
            Permutate(num);
            sf.delete(sf.length()-1,sf.length());
        }
    }

  
}