Merge pull request DaleStudy#2430 from j2h30728/main

SamTheKorean · web-flow · commit d7de405d1f59 · 2026-03-15T19:33:37.000-04:00
[j2h30728] Week 2 solutions
diff --git a/climbing-stairs/j2h30728.ts b/climbing-stairs/j2h30728.ts
@@ -0,0 +1,14 @@
+function climbStairs(n: number): number {
+  if (n === 0 || n === 1) {
+    return 1;
+  }
+
+  const memo: number[] = [];
+  memo[0] = memo[1] = 1;
+
+  for (let i = 2; i <= n; i++) {
+    memo[i] = memo[i - 1] + memo[i - 2];
+  }
+
+  return memo[n];
+}
diff --git a/product-of-array-except-self/j2h30728.ts b/product-of-array-except-self/j2h30728.ts
@@ -0,0 +1,18 @@
+function productExceptSelf(nums: number[]): number[] {
+  const length = nums.length;
+  const result = new Array(nums.length).fill(1);
+
+  let leftTemp = 1;
+  for (let i = 0; i < length; i++) {
+    result[i] = leftTemp;
+    leftTemp *= nums[i];
+  }
+
+  let rightTemp = 1;
+  for (let i = length - 1; i >= 0; i--) {
+    result[i] *= rightTemp;
+    rightTemp *= nums[i];
+  }
+
+  return result;
+}
diff --git a/valid-anagram/j2h30728.ts b/valid-anagram/j2h30728.ts
@@ -0,0 +1,12 @@
+function isAnagram(s: string, t: string): boolean {
+  const obj = {};
+  for (let i = 0; i < s.length; i++) {
+    obj[s[i]] = (obj[s[i]] || 0) + 1;
+  }
+
+  for (let i = 0; i < t.length; i++) {
+    obj[t[i]] -= 1;
+  }
+
+  return Object.values(obj).filter((value) => value !== 0).length === 0;
+}
diff --git a/validate-binary-search-tree/j2h30728.ts b/validate-binary-search-tree/j2h30728.ts
@@ -0,0 +1,22 @@
+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;
+  }
+}
+
+function isValidBST(root: TreeNode | null): boolean {
+  function valid(node, min, max) {
+    if (!node) return true;
+
+    if (node.val <= min || node.val >= max) return false;
+
+    return valid(node.left, min, node.val) && valid(node.right, node.val, max);
+  }
+
+  return valid(root, -Infinity, Infinity);
+}
