g0601_0700.s0623_add_one_row_to_tree.Solution Maven / Gradle / Ivy

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Java-based LeetCode algorithm problem solutions, regularly updated
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package g0601_0700.s0623_add_one_row_to_tree;

// #Medium #Depth_First_Search #Breadth_First_Search #Tree #Binary_Tree
// #2022_03_21_Time_0_ms_(100.00%)_Space_45.6_MB_(29.97%)

import com_github_leetcode.TreeNode;

/*
 * Definition for a binary tree node.
 * public class TreeNode {
 *     int val;
 *     TreeNode left;
 *     TreeNode right;
 *     TreeNode() {}
 *     TreeNode(int val) { this.val = val; }
 *     TreeNode(int val, TreeNode left, TreeNode right) {
 *         this.val = val;
 *         this.left = left;
 *         this.right = right;
 *     }
 * }
 */
/**
 * 623 - Add One Row to Tree\.
 *
 * Medium
 *
 * Given the `root` of a binary tree and two integers `val` and `depth`, add a row of nodes with value `val` at the given depth `depth`.
 *
 * Note that the `root` node is at depth `1`.
 *
 * The adding rule is:
 *
 * *   Given the integer `depth`, for each not null tree node `cur` at the depth `depth - 1`, create two tree nodes with value `val` as `cur`'s left subtree root and right subtree root.
 * *   `cur`'s original left subtree should be the left subtree of the new left subtree root.
 * *   `cur`'s original right subtree should be the right subtree of the new right subtree root.
 * *   If `depth == 1` that means there is no depth `depth - 1` at all, then create a tree node with value `val` as the new root of the whole original tree, and the original tree is the new root's left subtree.
 *
 * **Example 1:**
 *
 * ![](https://assets.leetcode.com/uploads/2021/03/15/addrow-tree.jpg)
 *
 * **Input:** root = [4,2,6,3,1,5], val = 1, depth = 2
 *
 * **Output:** [4,1,1,2,null,null,6,3,1,5]
 *
 * **Example 2:**
 *
 * ![](https://assets.leetcode.com/uploads/2021/03/11/add2-tree.jpg)
 *
 * **Input:** root = [4,2,null,3,1], val = 1, depth = 3
 *
 * **Output:** [4,2,null,1,1,3,null,null,1]
 *
 * **Constraints:**
 *
 * *   The number of nodes in the tree is in the range [1, 10⁴].
 * *   The depth of the tree is in the range [1, 10⁴].
 * *   `-100 <= Node.val <= 100`
 * *   -10⁵ <= val <= 10⁵
 * *   `1 <= depth <= the depth of tree + 1`
**/
public class Solution {
    public TreeNode addOneRow(TreeNode root, int val, int depth) {
        if (depth == 1) {
            TreeNode newRoot = new TreeNode(val);
            newRoot.left = root;
            return newRoot;
        }
        dfs(root, depth - 2, val);
        return root;
    }

    private void dfs(TreeNode node, int depth, int val) {
        if (depth == 0) {
            TreeNode left = new TreeNode(val);
            TreeNode right = new TreeNode(val);
            left.left = node.left;
            right.right = node.right;
            node.left = left;
            node.right = right;
        } else {
            if (node.left != null) {
                dfs(node.left, depth - 1, val);
            }
            if (node.right != null) {
                dfs(node.right, depth - 1, val);
            }
        }
    }
}