문제 설명
Given the root of a binary tree, invert the tree, and return its root.
Note: A leaf is a node with no children.
Example 1:
Input: root = [4,2,7,1,3,6,9]
Output: [4,7,2,9,6,3,1]
Example 2:
Input: root = [2,1,3]
Output: [2,3,1]
Example 3:
Input: root = []
Output: []
Constraints:
- The number of nodes in the tree is in the range
[0, 100]. -100 <= Node.val <= 100
문제풀이
BFS와 DFS 모두 구현하여 풀어보았다.
class Solution {
func BFS(_ root: TreeNode?) {
guard let root = root else { return }
var queue: [TreeNode] = [root]
while !queue.isEmpty {
for _ in queue {
let node = queue.removeFirst()
swap(&node.left, &node.right)
if let leftNode = node.left { queue.append(leftNode) }
if let rightNode = node.right { queue.append(rightNode) }
}
}
}
func DFS(_ root: TreeNode?) {
guard let root = root else { return }
swap(&root.right, &root.left)
DFS(root.left)
DFS(root.right)
}
func invertTree(_ root: TreeNode?) -> TreeNode? {
BFS(root)
//DFS(root)
return root
}
}