226. Invert Binary Tree

[Tcdian]

226. Invert Binary Tree

翻转一棵二叉树。

Example

Input:

     4
   /   \
  2     7
 / \   / \
1   3 6   9

Output:

     4
   /   \
  7     2
 / \   / \
9   6 3   1

[Tcdian]

Solution

• JavaScript Solution

/**
 * Definition for a binary tree node.
 * function TreeNode(val, left, right) {
 *     this.val = (val===undefined ? 0 : val)
 *     this.left = (left===undefined ? null : left)
 *     this.right = (right===undefined ? null : right)
 * }
 */
/**
 * @param {TreeNode} root
 * @return {TreeNode}
 */
var invertTree = function(root) {
    if (root === null) {
        return null;
    }
    const invertedLeft = invertTree(root.left);
    const invertedRight = invertTree(root.right);
    root.left = invertedRight;
    root.right = invertedLeft;
    return root;
};

• TypeScript Solution

/**
 * Definition for a binary tree node.
 * class TreeNode {
 *     val: number
 *     left: TreeNode | null
 *     right: TreeNode | null
 *     constructor(val?: number, left?: TreeNode | null, right?: TreeNode | null) {
 *         this.val = (val===undefined ? 0 : val)
 *         this.left = (left===undefined ? null : left)
 *         this.right = (right===undefined ? null : right)
 *     }
 * }
 */

function invertTree(root: TreeNode | null): TreeNode | null {
    if (root === null) {
        return null;
    }
    const invertedLeft = invertTree(root.left);
    const invertedRight = invertTree(root.right);
    root.left = invertedRight;
    root.right = invertedLeft;
    return root;
};