Find Bottom Left Tree Value

Raunit Verma September 08, 2021

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;
        
    }
};