PAT-1102（Invert a Binary Tree）+二叉树的镜像+层次遍历+中序遍历+已知树的结构构树

Invert a Binary Tree

pat-1102

import java.util.Arrays;
import java.util.Queue;
import java.util.Scanner;
import java.util.concurrent.LinkedBlockingQueue;

/**
 * @Author WaleGarrett
 * @Date 2020/9/5 20:04
 */
public class PAT_1102 {
    static InvertTree[] tree;
    static boolean[] flag;
    public static void main(String[] args) {
        Scanner scanner=new Scanner(System.in);
        int n=scanner.nextInt();
        tree=new InvertTree[n];
        flag=new boolean[n];
        Arrays.fill(flag,false);
        scanner.nextLine();
        for(int i=0;i<n;i++){
            String a=scanner.next(),b=scanner.next();
            int na,nb;
            if(a.equals("-")){
                na=-1;

            }else {
                na=Integer.parseInt(a);
                flag[na]=true;
            }
            if(b.equals("-")){
                nb=-1;
            }else {
                nb=Integer.parseInt(b);
                flag[nb]=true;
            }
            tree[i]=new InvertTree();
            tree[i].left=na;
            tree[i].right=nb;
        }
        int head=-1;
        for(int i=0;i<n;i++){
            if(!flag[i]){
                head=i;
                break;
            }
        }
        System.out.println(levelOrder(head,"").trim());
        System.out.println(inOrder(head,"").trim());
    }
    public static String levelOrder(int head,String result){
        Queue<Integer> que=new LinkedBlockingQueue<>();
        que.add(head);
        while(!que.isEmpty()){
            int now=que.poll();
            result=result+now+" ";
            if(tree[now].right!=-1) que.add(tree[now].right);
            if(tree[now].left!=-1) que.add(tree[now].left);
        }
        return result;
    }
    public static String inOrder(int head,String result){
        if(head==-1)
            return result;
        result=inOrder(tree[head].right,result);
        result=result+head+" ";
        result=inOrder(tree[head].left,result);
        return result;
    }
}
class InvertTree{
    int left,right,value;
}