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1.根据二叉树创建字符串

题目链接：. - 力扣（LeetCode）

class Solution {public String tree2str(TreeNode root) {if(root==null){return null;}StringBuilder stringBuilder=new StringBuilder();tree2strChild(root,stringBuilder);return stringBuilder.toString();}public void tree2strChild(TreeNode t,StringBuilder stringBuilder){if(t==null){return;}stringBuilder.append(t.val);if(t.left!=null){stringBuilder.append("(");tree2strChild(t.left,stringBuilder);stringBuilder.append(")");}else{if(t.right==null){return;}else{stringBuilder.append("()");}}if(t.right!=null){stringBuilder.append("(");tree2strChild(t.right,stringBuilder);stringBuilder.append(")");}else{return;}}
}

2.二叉树前序非递归遍历实现

题目链接：. - 力扣（LeetCode）

public void preOrderTree(TreeNode root){Stack<TreeNode> stack=new Stack<>();if(root==null){return ;}TreeNode cur=root;while (cur!=null || !stack.isEmpty()){while (cur!=null){stack.push(cur);System.out.println(cur.val+" ");cur=cur.left;}TreeNode top=stack.pop();cur=cur.right;}}

3.二叉树中序非递归遍历实现

题目链接：. - 力扣（LeetCode）

public void inOrderTree(TreeNode root){Stack<TreeNode> stack=new Stack<>();if(root==null){return ;}TreeNode cur=root;while (cur!=null || !stack.isEmpty()){while (cur!=null){stack.push(cur);cur=cur.left;}TreeNode top=stack.pop();System.out.println(top.val+" ");cur=cur.right;}}

4.二叉树后序非递归遍历实现

题目链接：. - 力扣（LeetCode）

public void postOrderTree(TreeNode root){Stack<TreeNode> stack=new Stack<>();if(root==null){return ;}TreeNode cur=root;TreeNode prev=null;while (cur!=null || !stack.isEmpty()){while (cur!=null){stack.push(cur);cur=cur.left;}TreeNode top=stack.peek();if(top.right==null || top.right==prev){System.out.println(top.val+" ");stack.pop();prev=top;}else {top=top.right;}}}

希望能对大家有所帮助！！！！