Add binary-tree-maximum-path-sum

Author: Jeehay28

binary-tree-maximum-path-sum/Jeehay28.js

@@ -0,0 +1,37 @@
+// ✅ Time Complexity: O(N) (Each node is visited once)
+// ✅ Space Complexity: O(N)
+
+/**
+ * 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 maxPathSum = function (root) {
+  let maxSum = -Infinity;
+
+  const dfs = (node) => {
+    if (!node) return 0;
+
+    let leftMax = Math.max(dfs(node.left), 0);
+    let rightMax = Math.max(dfs(node.right), 0);
+
+    // Compute best path sum that passes through this node
+    let currentMax = node.val + leftMax + rightMax;
+
+    // Update global maxSum
+    maxSum = Math.max(maxSum, currentMax); // represents the best path sum for the current node.
+
+    return node.val + Math.max(leftMax, rightMax); // propagates the maximum path sum to the parent node.
+  };
+
+  dfs(root);
+  return maxSum;
+};
+