Binary Tree Maximum Path Sum

Binary Tree Maximum Path Sum tree

Given a binary tree, find the maximum path sum.

For this problem, a path is defined as any sequence of nodes from some starting node to any node in the tree along the parent-child connections. The path must contain at least one node and does not need to go through the root.

For example:
Given the below binary tree,

        1
       / \
      2   3

Return 6.

Binary Tree Maximum Path Sum Solution

/**
 * Definition for a binary tree node.
 * public class TreeNode {
 *     int val;
 *     TreeNode left;
 *     TreeNode right;
 *     TreeNode(int x) { val = x; }
 * }
 */
public class BinaryTreeMaximumPathSum {
    int max = Integer.MIN_VALUE;

    public int maxPathSum(TreeNode root) {
        maxPathSumRecursive(root);
        return max;
    }

    private int maxPathSumRecursive(TreeNode root) {
        if(root == null) {
            return 0;
        }

        int left = Math.max(maxPathSumRecursive(root.left), 0);
        int right = Math.max(maxPathSumRecursive(root.right), 0);

        max = Math.max(max, root.val + left + right);

        return root.val + Math.max(left, right);
    }
}

Last modified October 4, 2020