LeetCode in Kotlin

572. Subtree of Another Tree

Easy

Given the roots of two binary trees root and subRoot, return true if there is a subtree of root with the same structure and node values of subRoot and false otherwise.

A subtree of a binary tree tree is a tree that consists of a node in tree and all of this node’s descendants. The tree tree could also be considered as a subtree of itself.

Example 1:

Input: root = [3,4,5,1,2], subRoot = [4,1,2]

Output: true

Example 2:

Input: root = [3,4,5,1,2,null,null,null,null,0], subRoot = [4,1,2]

Output: false

Constraints:

• The number of nodes in the root tree is in the range [1, 2000].
• The number of nodes in the subRoot tree is in the range [1, 1000].
• -104 <= root.val <= 104
• -104 <= subRoot.val <= 104

Solution

import com_github_leetcode.TreeNode

/*
 * Example:
 * var ti = TreeNode(5)
 * var v = ti.`val`
 * Definition for a binary tree node.
 * class TreeNode(var `val`: Int) {
 *     var left: TreeNode? = null
 *     var right: TreeNode? = null
 * }
 */
class Solution {
    private fun isSubtreeFound(root: TreeNode?, subRoot: TreeNode?): Boolean {
        if (root == null && subRoot == null) {
            return true
        }
        if (root == null || subRoot == null) {
            return false
        }
        return if (root.`val` == subRoot.`val`) {
            isSubtreeFound(root.left, subRoot.left) && isSubtree(root.right, subRoot.right)
        } else {
            false
        }
    }

    fun isSubtree(root: TreeNode?, subRoot: TreeNode?): Boolean {
        if (root == null && subRoot == null) {
            return true
        }
        return if (root == null || subRoot == null) {
            false
        } else isSubtreeFound(root, subRoot) ||
            isSubtree(root.left, subRoot) ||
            isSubtree(root.right, subRoot)
    }
}

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