Add binary-tree-maximum-path-sum solution in TS

Author: Jeehay28

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

@@ -0,0 +1,30 @@
+class TreeNode {
+  val: number;
+  left: TreeNode | null;
+  right: TreeNode | null;
+  constructor(val?: number, left?: TreeNode | null, right?: TreeNode | null) {
+    this.val = val === undefined ? 0 : val;
+    this.left = left === undefined ? null : left;
+    this.right = right === undefined ? null : right;
+  }
+}
+
+// TC: O(n)
+// SC: O(n)
+function maxPathSum(root: TreeNode | null): number {
+  let maxSum = -Infinity;
+
+  const dfs = (node: TreeNode | null) => {
+    if (!node) return 0;
+
+    const leftMax = Math.max(dfs(node.left), 0);
+    const rightMax = Math.max(dfs(node.right), 0);
+
+    maxSum = Math.max(node.val + leftMax + rightMax, maxSum);
+
+    return node.val + Math.max(leftMax, rightMax);
+  };
+
+  dfs(root);
+  return maxSum;
+}