872. Leaf-Similar Trees

LeetCode 872. Leaf-Similar Trees

Description

Consider all the leaves of a binary tree, from left to right order, the values of those leaves form a leaf value sequence .

For example, in the given tree above, the leaf value sequence is (6, 7, 4, 9, 8).

Two binary trees are considered leaf-similar if their leaf value sequence is the same.

Return true if and only if the two given trees with head nodes root1 and root2 are leaf-similar.

Example 1:

Input: root1 = [3,5,1,6,2,9,8,null,null,7,4], root2 = [3,5,1,6,7,4,2,null,null,null,null,null,null,9,8]
Output: true

Example 2:

Input: root1 = [1], root2 = [1]
Output: true

Constraints:

• The number of nodes in each tree will be in the range [1, 200].

• Both of the given trees will have values in the range [0, 200].

Tags

Tree, Depth-first Search

Solution

Obtain all leaves from both tree, respectively, then compare both leaves collections (arrays).

Complexity

• Time complexity: $O(n)$

• Space complexity: $O(n)$

Code

func leafSimilar(root1 *TreeNode, root2 *TreeNode) bool {
	var leaves1, leaves2 []int
	var getLeaves func(*TreeNode, *[]int)
	getLeaves = func(root *TreeNode, leaves *[]int) {
		if root == nil {
			return
		}
		if root.Left == nil && root.Right == nil {
			*leaves = append(*leaves, root.Val)
		}
		getLeaves(root.Left, leaves)
		getLeaves(root.Right, leaves)
	}
	getLeaves(root1, &leaves1)
	getLeaves(root2, &leaves2)
	if len(leaves1) == len(leaves2) {
		for i, n := range leaves1 {
			if leaves2[i] != n {
				return false
			}
		}
		return true
	}
	return false
}