二叉树的前序遍历、中序遍历、后序遍历、层序遍历

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原创最新推荐文章于 2026-06-23 09:25:56 发布 135 阅读 AI 写同款· GEO 优化 ›

二叉树及完全二叉树的前序遍历、中序遍历、后序遍历及层序遍历 本期主要分享的是树形结构的基本概念，树型结构中完全二叉树的创建以及二叉树的一些基本操作，其中主要包括了二叉树的创建，销毁以及二叉树的前序遍历中序遍历及后序遍历，主要用到的思想的函数递归思想，希望小伙伴们一定要注意基础知识的重要性，不能急于求成；加油小伙伴们！阅读详情

1.节点定义

public class TreeNode {
    public int val;
    public TreeNode left;
    public TreeNode right;


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

    public TreeNode(int val, TreeNode left, TreeNode right) {
        this.val = val;
        this.left = left;
        this.right = right;
    }
}

2.中序遍历

左-根-右

public static void printTreeInOrder(TreeNode root) {
    if (root == null) {
        return;
    }
    if (root.left != null) {
        printTreeInOrder(root.left);
    }
    System.out.print(root.val + "\t");
    if (root.right != null) {
        printTreeInOrder(root.right);
    }
}

3.先序遍历

根-左-右

public static void printTreePreOrder(TreeNode root) {
    if (root == null) {
        return;
    }
    System.out.print(root.val + "\t");
    if (root.left != null) {
        printTreePreOrder(root.left);
    }
    if (root.right != null) {
        printTreePreOrder(root.right);
    }
}

4.后序遍历

左-右-根

public static void printTreePostOrder(TreeNode root) {
    if (root == null) {
        return;
    }
    if (root.left != null) {
        printTreePostOrder(root.left);
    }
    if (root.right != null) {
        printTreePostOrder(root.right);
    }
    System.out.print(root.val + "\t");

}

5.层序遍历

利用队列

public static void printTreeLevelOrder(TreeNode root) {
    LinkedList<TreeNode> queue = new LinkedList<>();
    queue.offer(root);
    while (!queue.isEmpty()) {
        TreeNode current = queue.poll();
        System.out.print(current.val + "\t");
        if (current.left != null) {
            queue.offer(current.left);
        }
        if (current.right != null) {
            queue.offer(current.right);
        }
    }
    System.out.println();
}