找树左下角的值

// Solution in Java using Streams
// While Java Streams are more suited for working with collections, they can still be useful in other parts.
// However, we still need to use standard tree traversal techniques, as there is no built-in Stream operation for tree traversal.
// Thus, the main approach will remain the same as above, with minor stream usages.
 
import java.util.*;
 
class TreeNode {
    int val;
    TreeNode left;
    TreeNode right;
    TreeNode(int x) { val = x; }
}
 
public class Solution {
    public int findBottomLeftValue(TreeNode root) {
        Queue<TreeNode> queue = new LinkedList<>();
        queue.add(root);
        int result = root.val;
 
        while (!queue.isEmpty()) {
            // Stream usage for creating a list of nodes at current level
            List<TreeNode> levelNodes = queue.stream().toList();
            queue.clear();
            for (int i = 0; i < levelNodes.size(); i++) {
                TreeNode node = levelNodes.get(i);
                if (i == 0) {
                    result = node.val;  // update result with the first node's value in this level
                }
                if (node.left != null) queue.add(node.left);
                if (node.right != null) queue.add(node.right);
            }
        }
 
        return result;
    }
}