[算法][2]反转二叉树

前言

继续继续算法第二篇

题目

• 简单描述:

反转二叉树

问题详情
Invert Binary Tree.

解法:

1. 解法一 递归

    public TreeNode invertTree(TreeNode root) {
        if (root == null) {
            return null;
        }

        if (root.left != null) {
            invertTree(root.left);
        }
        if (root.right != null) {
            invertTree(root.right);
        }

        TreeNode treeNode = root.left;
        root.left = root.right;
        root.right = treeNode;

        return root;

    }

2. 解法二 非递归(经典解法)

public TreeNode invertTree(TreeNode root) {
    if (root == null) return null;
    Queue<TreeNode> queue = new LinkedList<TreeNode>();
    queue.add(root);
    while (!queue.isEmpty()) {
        TreeNode current = queue.poll();
        TreeNode temp = current.left;
        current.left = current.right;
        current.right = temp;
        if (current.left != null) queue.add(current.left);
        if (current.right != null) queue.add(current.right);
    }
    return root;
}

总结

算法贵在持之以恒,做多了 就懂了!继续干小伙伴们!!!