[JangAyeon] WEEK 01 solutions

contains-duplicate/JangAyeon.js

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+/**
+ * @param {number[]} nums
+ * @return {boolean}
+ */
+
+// 첫번째 제출
+var containsDuplicate = function (nums) {
+  const counter = new Map();
+  for (let e of nums) {
+    const v = counter.has(e) ? counter.get(e) + 1 : 1;
+    counter.set(e, v);
+  }
+  const answer = [...counter.values()].some((item) => item >= 2);
+  return answer;
+};
+// 두번째 제출
+var containsDuplicate = function (nums) {
+  return new Set(nums).size !== nums.length;
+};

house-robber/JangAyeon.js

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+/**
+ * @param {number[]} nums
+ * @return {number}
+ */
+var rob = function (nums) {
+  const N = nums.length;
+  let answer = 0;
+  let [rob1, rob2] = [0, 0];
+  for (let num of nums) {
+    let temp = Math.max(num + rob1, rob2);
+    rob1 = rob2;
+    rob2 = temp;
+  }
+  return rob2;
+};

longest-consecutive-sequence/JangAyeon.js

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+/**
+ * @param {number[]} nums
+ * @return {number}
+ */
+var longestConsecutive = function (nums) {
+  if (nums.length == 0) return 0;
+  let answer = 0;
+  let numsSet = new Set(nums);
+  const N = nums.length;
+
+  for (let num of numsSet) {
+    if (!numsSet.has(num - 1)) {
+      let temp = num;
+      let length = 1;
+
+      while (numsSet.has(temp + 1)) {
+        length += 1;
+        temp += 1;
+      }
+      // console.log(length)
+      answer = Math.max(length, answer);
+    }
+  }
+
+  return answer;
+};

top-k-frequent-elements/JangAyeon.js

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+/**
+ * @param {number[]} nums
+ * @param {number} k
+ * @return {number[]}
+ */
+var topKFrequent = function (nums, k) {
+  nums = nums.sort((a, b) => a - b);
+  const counter = new Map();
+  for (let num of nums) {
+    const value = counter.has(num) ? counter.get(num) + 1 : 1;
+    counter.set(num, value);
+  }
+  const sorted = [...counter.entries()].sort((a, b) => b[1] - a[1]);
+  const answer = sorted.slice(0, k).map((item) => item[0]);
+  // console.log(counter, sorted, answer)
+
+  return answer;
+};

two-sum/JangAyeon.js

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+/**
+ * @param {number[]} nums
+ * @param {number} target
+ * @return {number[]}
+ */
+
+// 첫번째 통과 풀이 - 브루트포스
+var twoSum = function (nums, target) {
+  for (let i = 0; i < nums.length; i++) {
+    for (let j = i + 1; j < nums.length; j++) {
+      if (nums[i] + nums[j] == target) {
+        return [i, j];
+      }
+    }
+  }
+};
+
+// 두번째 통과 풀이 - 해시맵 + 효율성 고려
+var twoSum = function (nums, target) {
+  const map = new Map(); // {값: 인덱스}
+
+  for (let i = 0; i < nums.length; i++) {
+    const complement = target - nums[i]; // 필요한 짝 계산
+    if (map.has(complement)) {
+      return [map.get(complement), i]; // 이전에 complement가 있었으면 바로 반환
+    }
+    map.set(nums[i], i);
+  }
+};