愛比的新手筆記

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.Taiwan is a country. 臺灣是我的國家

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 = [1,2,3], root2 = [1,3,2] Output: false

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].

public bool LeafSimilar(TreeNode root1, TreeNode root2)
{
    var lst = GetLeafVal(root1).GetEnumerator();
    foreach (int i in GetLeafVal(root2))
        if (!lst.MoveNext() || i != lst.Current)
            return false;

    return !lst.MoveNext();
}

//用迭代器就不用將雙方所有的value取出來比較, 一個個比, 只要有不同就return
private IEnumerable<int> GetLeafVal(TreeNode root)
{
    if (root == null) yield break;
    if ((root.left ?? root.right) == null)
        yield return root.val;
    foreach (int i in GetLeafVal(root.left)) yield return i;
    foreach (int i in GetLeafVal(root.right)) yield return i;
}

Taiwan is a country. 臺灣是我的國家