226 Invert Binary Tree

LeetCode

Given the root of a binary tree, invert the tree, and return its root.

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

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先把该节点的左右子树交换，再分别对左右子树操作

class Solution {
    public TreeNode invertTree(TreeNode root) {
        if(root==null) return null;
        TreeNode t=root.left;
        root.left=root.right;
        root.right=t;
        invertTree(root.left);
        invertTree(root.right);
        return root;
    }
}