513. Find Bottom Left Tree Value

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513. Find Bottom Left Tree Value

Description

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

Example 1:

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

Example 2:

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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, 10^4].
  • -2^31 <= Node.val <= 2^31 - 1

Hints/Notes

  • N/A

Solution

Language: C++

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/**
 * 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 = 0, depth = 0, res = 0;

    int findBottomLeftValue(TreeNode* root) {
        traverse(root);
        return res;
    }

    void traverse(TreeNode* root) {
        if (!root) {
            return;
        }
        depth++;
        if (depth > maxDepth) {
            maxDepth = depth;
            res = root->val;
        }
        traverse(root->left);
        traverse(root->right);
        depth--;
    }
};