513. Find Bottom Left Tree Value

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

Example 1:

Input:

2
/ \
1   3

Output:
1

Example 2:

Input:

1
/ \
2   3
/   / \
4   5   6
/
7

Output:
7

Note:You may assume the tree (i.e., the given root node) is not
NULL.

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Solution:

Tips:

recursion, root, right, left

Java Code:

/**
* Definition for a binary tree node.
* public 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<>();
TreeNode node = root;
queue.add(root);

while (!queue.isEmpty()) {
int queueSize = queue.size();
for (int i = 0; i < queueSize; i++) {
node = queue.poll();

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

return node.val;
}

}