Binary Tree Maximum Sum Path

MaximunSumPathBinaryTree.java

/**
 * Definition for binary tree
 * public class TreeNode {
 *     int val;
 *     TreeNode left;
 *     TreeNode right;
 *     TreeNode(int x) { val = x; }
 * }
 */
public class Solution {
    public int maxPathSum(TreeNode root) {
        if (root == null) return 0;
        if (root.left == null && root.right == null) return root.val;
        
        int[] max = {Integer.MIN_VALUE};
        
        maxPathSumHelper(root, max);
    
        return max[0];
        
    }
    
    public int maxPathSumHelper(TreeNode node, int[] max) {
        if (node == null) return Integer.MIN_VALUE;
        
        int left = maxPathSumHelper(node.left, max);
        int right = maxPathSumHelper(node.right, max);
        
        left = left > 0 ? left : 0;
        right = right > 0 ? right : 0;
        if (node.val + left + right > max[0]) {
            max[0] = node.val + left + right;
        }
        return node.val + Math.max(left, right);
        
    }
}