129. Sum Root to Leaf Numbers (axross#151)

Author: Kohei Asai

Diff for: solutions/sum_root_to_leaf_numbers.ts

@@ -0,0 +1,26 @@
+import { BinaryTreeNode } from "../data_structures/binary_tree.ts";
+
+// 129. Sum Root to Leaf Numbers
+// https://leetcode.com/problems/sum-root-to-leaf-numbers/
+export default function sumNumbers(
+  root: BinaryTreeNode<number> | null
+): number {
+  return sumNumbersWithContext(root, 0);
+}
+
+function sumNumbersWithContext(
+  node: BinaryTreeNode<number> | null,
+  contextSum: number
+): number {
+  if (node === null) return 0;
+
+  const hasChild = node.left !== null || node.right !== null;
+  const sum = contextSum * 10 + node.val;
+
+  if (!hasChild) return sum;
+
+  return (
+    sumNumbersWithContext(node.left, sum) +
+    sumNumbersWithContext(node.right, sum)
+  );
+}

Diff for: solutions/sum_root_to_leaf_numbers_test.ts

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+import { test } from "https://deno.land/std/testing/mod.ts";
+import { assertStrictEq } from "https://deno.land/std/testing/asserts.ts";
+import { createBinaryTreeNode } from "../data_structures/binary_tree.ts";
+import sumNumbers from "./sum_root_to_leaf_numbers.ts";
+
+test("129. Sum Root to Leaf Numbers", () => {
+  assertStrictEq(sumNumbers(createBinaryTreeNode([1, 2, 3])), 25);
+  assertStrictEq(sumNumbers(createBinaryTreeNode([4, 9, 0, 5, 1])), 1026);
+  assertStrictEq(sumNumbers(createBinaryTreeNode([0, 1])), 1);
+  assertStrictEq(sumNumbers(createBinaryTreeNode([])), 0);
+});