[ganu] Week1

contains-duplicate/gwbaik9717.js

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+// Time complexity: O(n)
+// Space complexity: O(n)
+
+/**
+ * @param {number[]} nums
+ * @return {boolean}
+ */
+var containsDuplicate = function (nums) {
+  const set = new Set(nums);
+
+  return set.size !== nums.length;
+};

house-robber/gwbaik9717.js

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+// Time complexity: O(n)
+// Space complexity: O(n)
+
+/**
+ * @param {number[]} nums
+ * @return {number}
+ */
+var rob = function (nums) {
+  const n = nums.length;
+  const dp = Array.from({ length: n + 1 }, () => 0);
+  dp[1] = nums[0];
+
+  for (let i = 2; i < n + 1; i++) {
+    dp[i] = Math.max(dp[i - 1], dp[i - 2] + nums[i - 1]);
+  }
+
+  return dp.at(-1);
+};

longest-consecutive-sequence/gwbaik9717.js

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+// Time complexity: O(n)
+// Space complexity: O(n)
+
+/**
+ * @param {number[]} nums
+ * @return {number}
+ */
+var longestConsecutive = function (nums) {
+  let answer = 0;
+  const consecutiveDict = new Map();
+
+  for (const num of nums) {
+    consecutiveDict.set(num, true);
+  }
+
+  for (const num of nums) {
+    if (consecutiveDict.has(num - 1)) {
+      continue;
+    }
+
+    let length = 1;
+    while (consecutiveDict.has(num + length)) {
+      length++;
+    }
+
+    answer = Math.max(answer, length);
+  }
+
+  return answer;
+};

top-k-frequent-elements/gwbaik9717.js

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+// Time complexity: O(nlogn)
+// Space complexity: O(n)
+
+/**
+ * @param {number[]} nums
+ * @param {number} k
+ * @return {number[]}
+ */
+var topKFrequent = function (nums, k) {
+  const frequencyDict = new Map();
+
+  for (const num of nums) {
+    if (frequencyDict.has(num)) {
+      frequencyDict.set(num, frequencyDict.get(num) + 1);
+    } else {
+      frequencyDict.set(num, 1);
+    }
+  }
+
+  const entries = [...frequencyDict.entries()];
+  entries.sort((a, b) => b[1] - a[1]);
+
+  return entries.slice(0, k).map((entry) => entry[0]);
+};

valid-palindrome/gwbaik9717.js

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+// Time complexity: O(n)
+// Space complexity: O(n)
+
+/**
+ * @param {string} s
+ * @return {boolean}
+ */
+var isPalindrome = function (s) {
+  const normalized = s.toLowerCase().replace(/[^a-z0-9]/g, "");
+  const reversed = normalized.split("").reverse().join("");
+
+  return normalized === reversed;
+};