> For the complete documentation index, see [llms.txt](https://nataliekung.gitbook.io/ladder_code/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://nataliekung.gitbook.io/ladder_code/dfs/find-bottom-left-tree-value.md).

# Find Bottom Left Tree Value

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**.

分析

bfs就是层遍历，注意每次弹出的是q\[0]

```
# Definition for a binary tree node.
# class TreeNode:
#     def __init__(self, x):
#         self.val = x
#         self.left = None
#         self.right = None

class Solution:
    def findBottomLeftValue(self, root: TreeNode) -> int:
        q = [root]
        res = None
        while q:
            size = len(q)
            res = q[0]
            for i in range(size):
                cur = q.pop(0)
                if cur.left:
                    q.append(cur.left)
                if cur.right:
                    q.append(cur.right)
        return res.val
```

DFS

哪个先突破新高度就是那个node，每次都是左边先

```
# Definition for a binary tree node.
# class TreeNode:
#     def __init__(self, x):
#         self.val = x
#         self.left = None
#         self.right = None

class Solution:
    def findBottomLeftValue(self, root: TreeNode) -> int:
        res,depth = root.val, 1
        def dfs(root:TreeNode,d:int):
            nonlocal depth,res
            if not root:
                return
            if depth < d:
                depth = d
                res = root.val
            dfs(root.left,d+1)
            dfs(root.right,d+1)
        dfs(root,1)
        return res
```


---

# Agent Instructions
This documentation is published with GitBook. GitBook is the documentation platform designed so that both humans and AI agents can read, navigate, and reason over technical content effectively. Learn more at gitbook.com.

## Querying This Documentation
If you need additional information that is not directly available in this page, you can query the documentation dynamically by asking a question.

Perform an HTTP GET request on the current page URL with the `ask` query parameter:

```
GET https://nataliekung.gitbook.io/ladder_code/dfs/find-bottom-left-tree-value.md?ask=<question>
```

The question should be specific, self-contained, and written in natural language.
The response will contain a direct answer to the question and relevant excerpts and sources from the documentation.

Use this mechanism when the answer is not explicitly present in the current page, you need clarification or additional context, or you want to retrieve related documentation sections.