LeetCode226-翻转二叉树

LeetCode226-翻转二叉树

前序遍历翻转

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//递归前序遍历进行交换
public TreeNode invertTree(TreeNode root) {
    if (root == null) {
        return null;
    }
    //交换左右结点
    TreeNode temp = root.left;
    root.left = root.right;
    root.right = temp;
    invertTree(root.left);
    invertTree(root.right);
    return root;
}

中序遍历翻转

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//递归中序遍历进行交换
public TreeNode invertTree(TreeNode root) {
    if (root == null) {
      return null;
    }
    invertTree(root.left);
    //交换左右结点
    TreeNode temp = root.left;
    root.left = root.right;
    root.right = temp;
    invertTree(root.left);
    return root;
}

后序遍历翻转

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//递归后序遍历进行交换
public TreeNode invertTree(TreeNode root) {
    if (root == null) {
      return null;
    }
    invertTree(root.left);
    invertTree(root.right);
    //交换左右结点
    TreeNode temp = root.left;
    root.left = root.right;
    root.right = temp;
    return root;
}

层序遍历翻转

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//层序遍历进行翻转左右子树
public TreeNode invertTree(TreeNode root) {
    if (root == null) {
        return null;
    }
    Queue<TreeNode> queue = new LinkedList<>();
    queue.offer(root);
    while (!queue.isEmpty()) {
        TreeNode node = queue.poll();
        TreeNode temp = node.left;
        node.left = node.right;
        node.right = temp;
        if (node.left != null) {
            queue.offer(node.left);
        }
        if (node.right != null) {
            queue.offer(node.right);
        }
    }
    return root;
}