LeetCode 513. Find the value in the lower left corner of the tree

513. Find the value in the lower left corner of the tree

 

【 Level traversal 】 Just find the value at the bottom of the last layer

/**
 * Definition for a binary tree node.
 * public class TreeNode {
 *     int val;
 *     TreeNode left;
 *     TreeNode right;
 *     TreeNode() {}
 *     TreeNode(int val) { this.val = val; }
 *     TreeNode(int val, TreeNode left, TreeNode right) {
 *         this.val = val;
 *         this.left = left;
 *         this.right = right;
 *     }
 * }
 */
class Solution {

    int bfs(TreeNode node){
        Queue<TreeNode> queue = new LinkedList();
        queue.offer(node);
        int ret = node.val;
        while(!queue.isEmpty()){
            int n = queue.size();
            for(var i = 0; i < n; i++){
                TreeNode top = queue.poll();
                if(i == 0) ret = top.val;
                if(top.left != null) queue.offer(top.left);
                if(top.right != null) queue.offer(top.right);
            }
        }
        return ret;
    }

    public int findBottomLeftValue(TreeNode root) {
        return bfs(root);
    }
}