题目链接/文章讲解/视频讲解：https://programmercarl.com/0513.%E6%89%BE%E6%A0%91%E5%B7%A6%E4%B8%8B%E8%A7%92%E7%9A%84%E5%80%BC.html

CPP

/**
 * Definition for a binary tree node.
 * struct TreeNode {
 *     int val;
 *     TreeNode *left;
 *     TreeNode *right;
 *     TreeNode() : val(0), left(nullptr), right(nullptr) {}
 *     TreeNode(int x) : val(x), left(nullptr), right(nullptr) {}
 *     TreeNode(int x, TreeNode *left, TreeNode *right) : val(x), left(left), right(right) {}
 * };
 */
class Solution {
public:
    int maxDepth = INT_MIN;
    int res;
    void traveral(TreeNode *node , int depth){
        
        if(node->left == NULL && node->right == NULL){
            if(depth > maxDepth){
                maxDepth = depth;
                res = node->val;
            }
        }
        if(node->left){
            depth++;
            traveral(node->left,depth);
            depth--;
        }
        if(node->right){
            depth++;
            traveral(node->right,depth);
            depth--;
        }
    }
    int findBottomLeftValue(TreeNode* root) {
        traveral(root,1);
        return res;
    }
};