Leetcode: binary tree 15 (find the value in the lower left corner of the tree)

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

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

Example 1:

Example 2:

… Isn't it the first in the last line of sequence traversal

package com.programmercarl.tree;

import java.util.ArrayDeque;
import java.util.Arrays;
import java.util.Deque;

/** * @ClassName FindBottomLeftValue * @Descriotion TODO * @Author nitaotao * @Date 2022/7/5 11:26 * @Version 1.0 * https://leetcode.cn/problems/find-bottom-left-tree-value/ * 513.  Find the value in the lower left corner of the tree  **/
public class FindBottomLeftValue {
    
    /** *  Given a binary tree   The root node  root, Please find the of the binary tree   At the bottom   Leftmost   The value of the node . *  Suppose there is at least one node in the binary tree . * <p> * .. Isn't it the first in the last line of sequence traversal  * @param root * @return */
    public int findBottomLeftValue(TreeNode root) {
    
        if (root.left == null && root.right == null) {
    
            return root.val;
        }
        int result = root.val;
        Deque<TreeNode> deque = new ArrayDeque();
        deque.offer(root);
        while (!deque.isEmpty()) {
    
            // The beginning of each floor 
            result = deque.peek().val;
            int size = deque.size();
            while (size > 0) {
    
                root = deque.pop();
                if (root.left != null) {
    
                    deque.offer(root.left);
                }
                if (root.right != null) {
    
                    deque.offer(root.right);
                }
                size--;
            }
            // End of each layer 
        }
        return result;
    }
}