import java.util.*;
/*
public class TreeNode {
    int val = 0;
    TreeNode left = null;
    TreeNode right = null;

    public TreeNode(int val) {
        this.val = val;

    }

}
*/
public class Solution {
    boolean isSymmetrical(TreeNode pRoot) {
     return  cheack(pRoot,pRoot);
        
        
    }
    boolean cheack(TreeNode a,TreeNode b) {
        if(a==null && b==null) return true;
        if(a==null||b==null) return false;
        if(a.val!=b.val) return false;
        return cheack(a.left,b.right)&cheack(a.right,b.left);
        
        
    }   
}

import java.util.*;


public class Solution {
    /**
     * 代码中的类名、方法名、参数名已经指定，请勿修改，直接返回方法规定的值即可
     *
     * 
     * @param str string字符串 
     * @return string字符串ArrayList
     */
    public ArrayList<String> Permutation (String str) {
        ArrayList<String> list=new ArrayList<>();
        StringBuilder sub= new StringBuilder();
        char strs[]=str.toCharArray();
        Arrays.sort(strs);
        dfs(list,sub,strs,0,new boolean[strs.length]);
        return list; 
        
    }
    
    void dfs(ArrayList<String> list,StringBuilder sub, char[]strs,int index,boolean[]vis){
        if(index==strs.length){
            list.add(sub.toString());
            return ;
            
        }
        for(int i=0;i<strs.length;i++){
            if(i>0 && strs[i-1]==strs[i]&&!vis[i-1]||vis[i])continue;
            sub.append(strs[i]);
            vis[i]=true; //用过的字符 标记为true
            dfs(list,sub,strs,index+1,vis);
            vis[i]=false;
            sub.deleteCharAt(index);
        }
        

    }
}

public class Solution {
    public int FirstNotRepeatingChar(String str) {
        int len=str.length();
        for(int i=0;i<len;i++){
            char ch=str.charAt(i);
            if(str.lastIndexOf(ch)==str.indexOf(ch))
            {
                return i;
            }
        }
        return -1;
        
        
    }
}

public class Solution {
    public int FirstNotRepeatingChar(String str) {
        int len=str.length();
        int map[]=new int[256];
        for(int i=0;i<len;i++){
            map[str.charAt(i)]++;
        }
        for(int i=0;i<len;i++){
            if( map[str.charAt(i)]==1){
                return i;
            }
        }
        
        return -1;
        
    }
}