题解 | #字符串的排列#

穷举，排列

排列之后，字符串有些是一样的，所有要有重操作

import java.util.ArrayList;
public class Solution {
//穷举
ArrayList<String> res;
String path;
int[] used;
public ArrayList<String> Permutation(String str) {
    res = new ArrayList<>();
    path = "";
    used = new int[str.length()];
    if(str.length() == 0) return res;
    track(str, path);
    return res;
}

public void track(String str, String path){
    if(path.length() == str.length()){
        if(!res.contains(path)) res.add(path);//去重
        return;
    }
    
    for(int i = 0; i < str.length(); i++){
        if(used[i] == 1) continue;
        used[i] = 1;
        track(str, path+str.charAt(i));
        used[i] = 0;//回溯
    }
}
}