Find Bottom Left Tree Value

 Find Bottom Left Tree Value

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

 

Example 1:

Input: root = [2,1,3]
Output: 1

Example 2:

Input: root = [1,2,3,4,null,5,6,null,null,7]
Output: 7

 

Constraints:

• The number of nodes in the tree is in the range [1, 104].
• -231 <= Node.val <= 231 - 1

Solution to the Above Question

/**

 * 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 findBottomLeftValue(TreeNode* root) {

        vector<int>temp;

        vector<vector<int>>v;

        if(root==NULL){

            return 0;

        }

        queue<TreeNode*>q;

        q.push(root);

        q.push(NULL);

        while(!q.empty()){

            TreeNode* f=q.front();

            q.pop();

            if(f==NULL){

                v.push_back(temp);

                temp.clear();

                if(!q.empty()){

                    q.push(NULL);

                }

            }

            else{

                temp.push_back(f->val);

                if(f->left){

                    q.push(f->left);

                }

                if(f->right){

                    q.push(f->right);

                }

            }

        }

        int k=v.size();

        int answer=v[k-1][0];

        return answer;

        

    }

};