二叉树oj ----＞ 二叉树的构建及遍历

Posted 2021-12-07 ohana！

题目内容：

 解题代码：

import java.util.*;

public class Main{
    public class TreeNode{
        char value;
        TreeNode left;
        TreeNode right;
        public TreeNode(char value){
            this.value = value;
        }
    }
    
    //给一个方法，给创建二叉树的方法包装一下
    TreeNode root;
    int index = 0;
    public void createBinaryTreeTest(String str,char invalid){
        index = 0;
        root = createBinaryTree(str,invalid);
    }
    
    // 创建二叉树
    public TreeNode createBinaryTree(String str,char invalid){
        TreeNode treeRoot = null;
        if(index < str.length() && str.charAt(index)!= invalid){
            treeRoot = new TreeNode(str.charAt(index));
            
            ++index;
            treeRoot.left = createBinaryTree(str,invalid);
            
            ++index;
            treeRoot.right = createBinaryTree(str,invalid);
        }
        return treeRoot;
    }
    
    public void inOrder(){
        inOrder(root);
    }
    
    //中序遍历
    public void inOrder(TreeNode treeRoot){
        if(treeRoot == null){
            return;
        }
        
        Stack<TreeNode> s = new Stack<>();
        TreeNode cur = treeRoot;
        while(!s.empty() || cur != null){
            while(cur != null){
                s.push(cur);
                cur = cur.left;
            }
            
            cur = s.pop();
            System.out.print(cur.value + " ");
            cur = cur.right;
        }
    }
    public static void main(String[] args){
        Scanner sc = new Scanner(System.in);
        while(sc.hasNext()){
            String str = sc.nextLine();
            Main m = new Main();
            m.createBinaryTreeTest(str,'#');
            m.inOrder();
        }
    }
}

解题步骤：

1. 首先给出树节点， 结点值的类
2. 给出构建二叉树的方法
3. 给出中序遍历的方法（不论是递归还是非递归都可以）