Binary Tree Maximum Path Sum

Author: TonyKim9401

binary-tree-maximum-path-sum/TonyKim9401.java

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+// TC: O(n)
+// visit all nodes to find maximum path
+// SC: O(h)
+// h means the high of binary tree
+class Solution {
+    private int output = Integer.MIN_VALUE;
+    public int maxPathSum(TreeNode root) {
+        max(root);
+        return output;
+    }
+
+    private int max(TreeNode node) {
+        if (node == null) return 0;
+
+        int leftSum = Math.max(max(node.left), 0);
+        int rightSum = Math.max(max(node.right), 0);
+
+        int currentMax = node.val + leftSum + rightSum;
+
+        output = Math.max(output, currentMax);
+
+        return node.val + Math.max(leftSum, rightSum);
+    }
+}