[froggy1014] WEEK 01 Solutions

contains-duplicate/froggy1014.js

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+// Set을 사용한 중복값 제거 후 길이 비교
+function containsDuplicate(nums) {
+  const numSet = new Set(nums);
+  return numSet.size !== nums.length;
+}
+
+console.log(containsDuplicate([1, 2, 3, 1])); // true
+console.log(containsDuplicate([1, 2, 3, 4])); // false
+console.log(containsDuplicate([1, 1, 1, 3, 3, 4, 3, 2, 4, 2])); // true

house-robber/froggy1014.js

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+/**
+ * @param {number[]} nums
+ * @return {number}
+ */
+var rob = function (nums) {
+  if (nums.length === 0) return 0;
+  if (nums.length === 1) return nums[0];
+
+  const dp = new Array(nums.length + 1);
+  dp[0] = 0;
+  dp[1] = nums[0];
+  for (let i = 2; i < dp.length; i++) {
+    dp[i] = Math.max(dp[i - 1], dp[i - 2] + nums[i - 1]);
+  }
+  return dp[dp.length - 1];
+};
+
+const nums = [2, 7, 9, 3, 1];
+
+console.log(rob(nums));

longest-consecutive-sequence/froggy1014.js

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+/**
+ * @param {number[]} nums
+ * @return {number}
+ */
+
+// 시간복잡도: O(n)
+var longestConsecutive = function (nums) {
+  let longest = 0;
+
+  let set = new Set(nums);
+
+  for (let num of nums) {
+    if (set.has(num - 1)) {
+      continue;
+    }
+
+    let count = 1;
+    let currentNum = num;
+
+    while (set.has(currentNum + 1)) {
+      count++;
+      currentNum++;
+    }
+    longest = Math.max(longest, count);
+  }
+  return longest;
+};
+
+console.log(longestConsecutive([100, 4, 200, 1, 3, 2])); // 4
+console.log(longestConsecutive([0, 3, 7, 2, 5, 8, 4, 6, 0, 1])); // 9
+console.log(longestConsecutive([1, 0, 1, 2])); // 3

top-k-frequent-elements/froggy1014.js

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+/**
+ * @param {number[]} nums
+ * @param {number} k
+ * @return {number[]}
+ */
+var topKFrequent = function (nums, k) {
+  const map = new Map();
+  for (let n = 0; n < nums.length; n++) {
+    map.has(nums[n])
+      ? map.set(nums[n], map.get(nums[n]) + 1)
+      : map.set(nums[n], 1);
+  }
+
+  return Array.from(map.entries())
+    .sort(([key1, value1], [key2, value2]) => value2 - value1)
+    .slice(0, k)
+    .map((v) => v[0]);
+};
+
+console.log(topKFrequent([1, 1, 1, 2, 2, 3], 2));

two-sum/froggy1014.js

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+/**
+ * @param {number[]} nums
+ * @param {number} target
+ * @return {number[]}
+ */
+var twoSum = function (nums, target) {
+  let map = new Map();
+  for (let idx = 0; idx < nums.length; idx++) {
+    const rest = target - nums[idx];
+    if (map.has(rest)) {
+      return [map.get(rest), idx];
+    }
+    map.set(nums[idx], idx);
+  }
+  return [];
+};
+
+console.log(twoSum([2, 11, 15, 7], 9));