Leetcode•Jul 01, 2025
Binary Tree Maximum Path Sum
Hazrat Ali
Leetcode
A path in a binary tree is a sequence of nodes where each pair of adjacent nodes in the sequence has an edge connecting them. A node can only appear in the sequence at most once. Note that the path does not need to pass through the root.
The path sum of a path is the sum of the node's values in the path.
Given the root of a binary tree, return the maximum path sum of any non-empty path.
Example 1:
Input: root = [1,2,3] Output: 6 Explanation: The optimal path is 2 -> 1 -> 3 with a path sum of 2 + 1 + 3 = 6.
Example 2:
Input: root = [-10,9,20,null,null,15,7] Output: 42 Explanation: The optimal path is 15 -> 20 -> 7 with a path sum of 15 + 20 + 7 = 42.
Solution
/**
* @param {TreeNode} root
* @return {number}
*/
const maxPathSum = root => {
const helper = root => {
if (!root) {
return 0;
}
const left = Math.max(helper(root.left), 0);
const right = Math.max(helper(root.right), 0);
max = Math.max(max, root.val + left + right);
return root.val + Math.max(left, right);
};
let max = Number.MIN_SAFE_INTEGER;
helper(root);
return max;
};