[byol-han] WEEK 15 solutions

binary-tree-level-order-traversal/byol-han.js

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+/**
+ * https://leetcode.com/problems/binary-tree-level-order-traversal/description/
+ * 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 levelOrder = function (root) {
+  const result = [];
+  if (!root) return result;
+
+  const queue = [root];
+
+  while (queue.length > 0) {
+    const levelSize = queue.length;
+    const level = [];
+
+    for (let i = 0; i < levelSize; i++) {
+      const node = queue.shift();
+      level.push(node.val);
+
+      if (node.left) queue.push(node.left);
+      if (node.right) queue.push(node.right);
+    }
+
+    result.push(level);
+  }
+
+  return result;
+};

house-robber-ii/byol-han.js

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+/**
+ * https://leetcode.com/problems/house-robber-ii/submissions/1686583649/
+ * @param {number[]} nums
+ * @return {number}
+ */
+var rob = function (nums) {
+  if (nums.length === 1) return nums[0];
+
+  // Helper to solve the linear house robber problem
+  function robLinear(houses) {
+    let prev1 = 0; // dp[i-1]
+    let prev2 = 0; // dp[i-2]
+
+    for (let money of houses) {
+      let temp = prev1;
+      prev1 = Math.max(prev1, prev2 + money);
+      prev2 = temp;
+    }
+
+    return prev1;
+  }
+
+  // Case 1: Exclude last house
+  let money1 = robLinear(nums.slice(0, nums.length - 1));
+  // Case 2: Exclude first house
+  let money2 = robLinear(nums.slice(1));
+
+  return Math.max(money1, money2);
+};

subtree-of-another-tree/byol-han.js

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+/**
+ * https://leetcode.com/problems/subtree-of-another-tree/description/
+ * 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
+ * @param {TreeNode} subRoot
+ * @return {boolean}
+ */
+var isSubtree = function (root, subRoot) {
+  // If the main tree is empty, it can't contain subRoot
+  if (!root) return false;
+
+  // If the trees rooted at current node are the same, return true
+  if (isSameTree(root, subRoot)) {
+    return true;
+  }
+
+  // Otherwise, recursively check left and right subtrees
+  return isSubtree(root.left, subRoot) || isSubtree(root.right, subRoot);
+};
+
+function isSameTree(s, t) {
+  // If both nodes are null, trees are identical at this branch
+  if (!s && !t) return true;
+
+  // If only one is null, trees are not identical
+  if (!s || !t) return false;
+
+  // If current node values are different, trees are not identical
+  if (s.val !== t.val) return false;
+
+  // Recursively check left and right children
+  return isSameTree(s.left, t.left) && isSameTree(s.right, t.right);
+}