java实现二叉树的子树交换的递归与非递归写法

最新推荐文章于 2025-07-17 17:42:40 发布

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本文介绍了两种实现二叉树节点左右子树交换的方法：一种是递归方式，另一种是非递归方式，后者利用栈来辅助完成。通过具体实例展示了算法效果。

递归程序：

class TreeNode{
	TreeNode left;
	TreeNode right;
	int data;
}
public class Tree1 {
	public static void Exchange(TreeNode head){
		if(null==head||(head.left==null&&head.right==null)){
			return;
		}
		TreeNode p = head.left;
		head.left=head.right;
		head.right=p;
		if(head.left!=null){
			Exchange(head.left);
		}
		if(head.right!=null){
			Exchange(head.right);
		}
		return;
	}
	public static TreeNode buildTree() {  
        TreeNode root = new TreeNode();  
        root.data = 1;  
  
        TreeNode temp = new TreeNode();  
        temp.data = 2;  
        root.left = temp;  
  
        temp = new TreeNode();  
        temp.data = 3;  
        root.right = temp;  
  
        temp = new TreeNode();  
        temp.data = 4;  
        root.right.right = temp;  
  
        temp = new TreeNode();  
        temp.data = 5;  
        root.left.right = temp;  
  
        temp = new TreeNode();  
        temp.data = 6;  
        root.left.right.right = temp;  
  
        return root;  
    } 
	public static void inOrderVisit(TreeNode root) {  
        if (root == null)  
            return;  
        inOrderVisit(root.left);  
        System.out.print(root.data);  
        inOrderVisit(root.right);  
    }  
	public static void main(String[] args){
		TreeNode root = buildTree();
		inOrderVisit(root);
		Exchange(root);
		System.out.println();
		inOrderVisit(root);
	}
}

非递归程序：

import java.util.Stack;

class TreeNode{
	TreeNode left;
	TreeNode right;
	int data;
}
public class Tree2 {
	public static void swapTree(TreeNode root){
		Stack<TreeNode> s = new Stack<TreeNode>();
		TreeNode p;
		if(null==root)return;
		s.push(root);
		while(!s.isEmpty()){
			root = s.pop();
			p = root.left;
			root.left=root.right;
			root.right=p;
			if(root.left!=null){
				s.push(root.left);
			}
			if(root.right!=null){
				s.push(root.right);
			}
		}
	}
	public static TreeNode buildTree() {  
        TreeNode root = new TreeNode();  
        root.data = 1;  
  
        TreeNode temp = new TreeNode();  
        temp.data = 2;  
        root.left = temp;  
  
        temp = new TreeNode();  
        temp.data = 3;  
        root.right = temp;  
  
        temp = new TreeNode();  
        temp.data = 4;  
        root.right.right = temp;  
  
        temp = new TreeNode();  
        temp.data = 5;  
        root.left.right = temp;  
  
        temp = new TreeNode();  
        temp.data = 6;  
        root.left.right.right = temp;  
  
        return root;  
    } 
	public static void inOrderVisit(TreeNode root) {  
        if (root == null)  
            return;  
        inOrderVisit(root.left);  
        System.out.print(root.data);  
        inOrderVisit(root.right);  
    }  
	public static void main(String[] args){
		TreeNode root = buildTree();
		inOrderVisit(root);
		swapTree(root);
		System.out.println();
		inOrderVisit(root);
	}
}

非递归算法使用了栈这种数据结构。