Merge branch 'main' into ohchaeyeon

Author: oh-chaeyeon

JooKangSan/[week6]Set/Character_that_appears_only_once.js

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+function solution(s) {
+  return s
+      .split('')
+      .sort()
+      .filter((char, idx, arr) => 
+          char !== arr[idx-1] && char !== arr[idx+1]
+      )
+      .join('');
+}
+// 시간 복잡도 o(n log n)
+// 공간 복잡도 o(n)

JooKangSan/[week6]Set/Contains_Duplicate.js

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+/**
+ * @param {number[]} nums
+ * @return {boolean}
+ */
+var containsDuplicate = function (nums) {
+  const uniqueNums = [...new Set(nums)];
+  return uniqueNums.length != nums.length;
+};

JooKangSan/[week6]Set/Longest_Consecutive_Sequence.js

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+/**
+ * @param {number[]} nums
+ * @return {number}
+ */
+var longestConsecutive = function (nums) {
+  const numSet = new Set(nums);
+  let longestStreak = 0;
+  for (const num of numSet) {
+    if (!numSet.has(num - 1)) {
+      let currentNum = num;
+      let currentStreak = 1;
+      while (numSet.has(currentNum + 1)) {
+        currentNum += 1;
+        currentStreak += 1;
+      }
+      longestStreak = Math.max(longestStreak, currentStreak);
+    }
+  }
+  return longestStreak;
+};

JooKangSan/[week6]Set/Prime_Factorization.js

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+function solution(n) {
+  let primeFactors = new Set();
+  let num = n;
+  
+  while(num % 2 === 0) {
+      primeFactors.add(2);
+      num = num / 2;
+  }
+     for(let i = 3; i <= num; i += 2) {
+      while(num % i === 0) {
+          primeFactors.add(i);
+          num = num / i;
+      }
+  }
+  if(num > 2) {
+      primeFactors.add(num);
+  }
+  
+  return [...primeFactors].sort((a, b) => a - b);
+}

JooKangSan/[week6]Set/Randomly_draw_K_numbers.js

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+function solution(arr, k) {
+  var answer = [...new Set(arr)];
+    return [...answer.slice(0, k), ...Array(Math.max(0, k - answer.length)).fill(-1)];
+}

JooKangSan/[week6]Set/Remove_duplicate_characters.js

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+function solution(my_string) {
+  var answer = [...new Set(my_string)].join('');
+  return answer;
+}

JooKangSan/[week6]Set/Repeated_DNA_Sequences.js

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+/**
+ * @param {string} s
+ * @return {string[]}
+ */
+function findRepeatedDnaSequences(s) {
+  const see = new Set();
+  const seen = new Set();
+
+  for (let i = 0; i <= s.length - 10; i++) {
+    const sequence = s.slice(i, i + 10);
+    if (see.has(sequence)) {
+      seen.add(sequence);
+    }
+    see.add(sequence);
+  }
+
+  return [...seen];
+}

JooKangSan/[week6]Set/Set.md

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+## 1. Set(집합)
+- 중복을 허용하지 않는 값들의 모음을 표현하는 자료구조,
+- 수학의 집합 개념을 구현한 자료구조
+
+## 2. Set 구현
+
+### 2.1 기본 생성
+```javascript
+// Set 생성
+const set = new Set();
+const setFromArray = new Set([1, 2, 3]);
+
+// 값 추가/삭제
+set.add(4);         // 값 추가
+set.delete(4);      // 값 삭제
+set.clear();        // 모든 값 삭제
+
+// 값 확인
+set.has(4);         // 값 존재 여부
+set.size;           // Set 크기
+```
+
+### 2.2 기본 연산
+```javascript
+class CustomSet {
+    constructor() {
+        this.items = {};
+    }
+    
+    // 원소 추가
+    add(element) {
+        if (!this.has(element)) {
+            this.items[element] = element;
+            return true;
+        }
+        return false;
+    }
+    
+    // 원소 삭제
+    delete(element) {
+        if (this.has(element)) {
+            delete this.items[element];
+            return true;
+        }
+        return false;
+    }
+    
+    // 원소 확인
+    has(element) {
+        return element in this.items;
+    }
+    
+    // 모든 원소 반환
+    values() {
+        return Object.values(this.items);
+    }
+}
+```
+
+## 3. Set 연산 메서드
+
+### 3.1 합집합(Union)
+```javascript
+function union(setA, setB) {
+    const unionSet = new Set(setA);
+    for (const element of setB) {
+        unionSet.add(element);
+    }
+    return unionSet;
+}
+```
+
+### 3.2 교집합(Intersection)
+```javascript
+function intersection(setA, setB) {
+    const intersectionSet = new Set();
+    for (const element of setA) {
+        if (setB.has(element)) {
+            intersectionSet.add(element);
+        }
+    }
+    return intersectionSet;
+}
+```
+
+### 3.3 차집합(Difference)
+```javascript
+function difference(setA, setB) {
+    const differenceSet = new Set(setA);
+    for (const element of setB) {
+        differenceSet.delete(element);
+    }
+    return differenceSet;
+}
+```
+
+### 3.4 부분집합(Subset) 확인
+```javascript
+function isSubset(setA, setB) {
+    for (const element of setA) {
+        if (!setB.has(element)) {
+            return false;
+        }
+    }
+    return true;
+}
+```
+
+## 4. Set 활용
+
+### 4.1 배열 중복 제거
+```javascript
+function removeDuplicates(array) {
+    return [...new Set(array)];
+}
+
+// 예시
+const array = [1, 2, 2, 3, 3, 4];
+console.log(removeDuplicates(array)); // [1, 2, 3, 4]
+```
+
+### 4.2 문자열 중복 문자 제거
+```javascript
+function removeDuplicateChars(str) {
+    return [...new Set(str)].join('');
+}
+
+// 예시
+console.log(removeDuplicateChars('hello')); // 'helo'
+```
+
+## 5. 성능 고려사항
+
+### 5.1 시간 복잡도
+- 추가(add): O(1)
+- 삭제(delete): O(1)
+- 검색(has): O(1)
+- 크기 확인(size): O(1)
+
+### 5.2 공간 복잡도
+- O(n), n은 저장된 원소의 수

JustDevRae/Set/contains_duplicate.js

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+var containsDuplicate = function (nums) {
+  const numSet = new Set(nums);
+  return numSet.size !== nums.length;
+};

JustDevRae/Set/pick_random_k_numbers.js

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+function solution(arr, k) {
+  const uniqueSet = new Set();
+  const result = [];
+
+  for (const num of arr) {
+    if (!uniqueSet.has(num)) {
+      uniqueSet.add(num);
+      result.push(num);
+    }
+    if (result.length === k) break;
+  }
+
+  while (result.length < k) {
+    result.push(-1);
+  }
+
+  return result;
+}