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

答案

class Solution {
    public int findBottomLeftValue(TreeNode root) {
        if(root == null) return -1;
        Queue<TreeNode> q = new LinkedList<TreeNode>();
        q.offer(root);
        int candidate = -1;
        while(q.size() != 0) {
            int curr_size = q.size();
            for(int i = 0; i < curr_size; i++) {
                TreeNode t = q.poll();
                if(i == 0)
                    candidate = t.val;
                if(t.left != null) q.offer(t.left);
                if(t.right != null) q.offer(t.right);
            }
        }
        return candidate;
    }
}