Problem
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
/**
* Definition for a binary tree node.
* function TreeNode(val, left, right) {
* this.val = (val===undefined ? 0 : val)
* this.left = (left===undefined ? null : left)
* this.right = (right===undefined ? null : right)
* }
*/
/**
* @param {TreeNode} root
* @return {number}
*/
var findBottomLeftValue = function(root) {
return dfs(root, 0)[0];
};
var dfs = function(node, depth) {
var left = node.left ? dfs(node.left, depth + 1) : [node.val, depth];
var right = node.right ? dfs(node.right, depth + 1) : [node.val, depth];
return right[1] > left[1] ? right : left;
};
Explain:
nope.
Complexity:
- Time complexity : O(n).
- Space complexity : O(1).