226. Invert Binary Tree

Easy
Given the root of a binary tree, invert the tree, and return its root.
Example 1:
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Input: root = [4,2,7,1,3,6,9]
Output: [4,7,2,9,6,3,1]
Example 2:
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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

解題

/**
* Definition for a binary tree node.
* type TreeNode struct {
* Val int
* Left *TreeNode
* Right *TreeNode
* }
*/
func invertTree(root *TreeNode) *TreeNode {
invert(root)
return root
}
​
func invert(root *TreeNode) {
if root != nil {
invert(root.Left)
invert(root.Right)
root.Left, root.Right = root.Right, root.Left
}
}