题目描述
给你一棵二叉树的根节点 root ，翻转这棵二叉树，并返回其根节点。
示例
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| 输入：root = [4,2,7,1,3,6,9]
输出：[4,7,2,9,6,3,1]
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提示：
- 树中节点数目范围在
[0, 100] 内
-100 <= Node.val <= 100
题解
方法1：遍历
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| func invertTree(_ root: TreeNode?) -> TreeNode? {
guard let root = root else {
return nil
}
var queue = [root]
while !queue.isEmpty {
let cur = queue.removeFirst()
let temp = cur.left
cur.left = cur.right
cur.right = temp
if let left = cur.left {
queue.append(left)
}
if let right = cur.right {
queue.append(right)
}
}
return root
}
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方法2：递归
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| func invertTree2(_ root: TreeNode?) -> TreeNode? {
guard let root = root else {
return root
}
let temp = root.left
root.left = root.right
root.right = temp
invertTree2(root.left)
invertTree2(root.right)
return root
}
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