513.find-bottom-left-tree-value.java

/*
 * @lc app=leetcode id=513 lang=java
 *
 * [513] Find Bottom Left Tree Value
 *
 * https://leetcode.com/problems/find-bottom-left-tree-value/description/
 *
 * algorithms
 * Medium (58.26%)
 * Likes:    577
 * Dislikes: 98
 * Total Accepted:    73.4K
 * Total Submissions: 125.1K
 * Testcase Example:  '[2,1,3]'
 *
 *
 * 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.
 *
 */
/**
 * Definition for a binary tree node.
 * public class TreeNode {
 *     int val;
 *     TreeNode left;
 *     TreeNode right;
 *     TreeNode(int x) { val = x; }
 * }
 */
class Solution {
  public int findBottomLeftValue(TreeNode root) {
    Queue<TreeNode> queue = new LinkedList<>();
    queue.offer(root);
    int value = -1;

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

    return value;
  }
}