0513_Find_Bottom_Left_Tree_Value.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:
    void solve(TreeNode* root, vector<int>& res, int l){
        if(root==NULL){
            return;
        }
        if(res.size()==l){
            res.push_back(root->val);
        }
        solve(root->left, res, l+1);
        solve(root->right, res, l+1);
    }
    int findBottomLeftValue(TreeNode* root) {
        vector<int>res;
        solve(root, res, 0);
        return res[res.size()-1];
    }
};