层序一遍过了
时间好像略高
也可以用dfs，感觉和树的左视图很像
/**
* 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 {
public int findBottomLeftValue(TreeNode root) {
if(root==null) return 0;
Queue<TreeNode> q = new LinkedList<>();
q.add(root);
int res = root.val;
while(!q.isEmpty()){
int s = q.size();
for(int i=0; i<s; i++){
TreeNode node = q.poll();
if(i==0) res = node.val;
if(node.left!=null) q.add(node.left);
if(node.right!=null) q.add(node.right);
}
}
return res;
}
}
