513. Find Bottom Left Tree Value

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LeetCode

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Problem

Given the root of a binary tree, return the leftmost value in the last row of the tree.

Example 1:

Input: root = [2,1,3]
Output: 1

Example 2:

Input: root = [1,2,3,4,null,5,6,null,null,7]
Output: 7

Constraints:

• The number of nodes in the tree is in the range [1, 10^4].
• -2^31 <= Node.val <= 2^31 - 1

Code

class Solution {
    public int findBottomLeftValue(TreeNode root) {
        if(root == null) return -1;

        Queue<TreeNode> queue = new LinkedList<>();
        queue.offer(root);
        
        while(!queue.isEmpty()) {
            root = queue.poll();

            if(root.right != null) queue.offer(root.right);
            if(root.left != null) queue.offer(root.left);
        }

        return root.val;
    }
}

class Solution {
    public int findBottomLeftValue(TreeNode root) {
        if(root == null) return -1;

        Queue<TreeNode> queue = new LinkedList<>();
        queue.offer(root);

        int left = root.val;
        
        while(!queue.isEmpty()) {
            int size = queue.size();
            
            for(int i = 0; i < size; i++) {
                TreeNode node = queue.poll();
                
                if(i == 0) {
                    left = node.val;
                }

                if(node.left != null) queue.offer(node.left);
                if(node.right != null) queue.offer(node.right);
            }
        }

        return left;
    }
}