Merge branch 'DaleStudy:main' into main

Author: toychip

best-time-to-buy-and-sell-stock/soobing.ts

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+function maxProfit(prices: number[]): number {
+  let minPrice = Infinity;
+  let maxProfit = 0;
+  for (let i = 0; i < prices.length; i++) {
+    if (prices[i] < minPrice) {
+      minPrice = prices[i];
+    }
+
+    if (prices[i] - minPrice > maxProfit) {
+      maxProfit = prices[i] - minPrice;
+    }
+  }
+  return maxProfit;
+}

contains-duplicate/JANGSEYEONG.js

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+/*
+  시간복잡도: O(n) - new Set(nums)에서 배열 요소 순회하며 Set 생성 O(n) + 길이 비교 O(1)
+  - Set 자료구조는 중복된 값을 자동으로 제거
+*/
+
+/**
+ * @param {number[]} nums
+ * @return {boolean}
+ */
+var containsDuplicate = function (nums) {
+  // Set으로 만들었을 때, 기존 배열과 사이즈가 다르면 중복이 제거된거임
+  const numsSet = new Set(nums);
+  return nums.length !== numsSet.size;
+};

contains-duplicate/Jeehay28.ts

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+// Approach 3: HashSet (Using TypeScript Set)
+// ⏳ Time Complexity: O(n)
+// 💾 Space Complexity: O(n)
+
+function containsDuplicate(nums: number[]): boolean {
+
+    const seen = new Set<number>();
+
+    for (const num of nums) {
+        if (seen.has(num)) {
+            return true;
+        }
+        seen.add(num);
+    }
+
+    return false;
+
+};
+
+
+// Approach 2: Sorting + Scan
+// ⏳ Time Complexity: O(n * log(n)) ❌ (Faster than O(n^2), but still not optimal)
+// 💾 Space Complexity: O(1)
+
+// function containsDuplicate(nums: number[]): boolean {
+
+//     nums.sort();
+
+//     for (let i = 0; i < nums.length - 1; i++) {
+//         if (nums[i] === nums[i + 1]) {
+//             return true;
+//         }
+//     }
+
+//     return false;
+
+// };
+
+
+// Approach 1: Brute Force (O(n^2))
+// 🚨⏳ TLE (Time Limit Exceeded)!
+// ⏳ Time Complexity: O(n^2) ❌ (Inefficient for large inputs)
+// 💾 Space Complexity: O(1) ✅ (Great, no extra memory used!)
+
+// function containsDuplicate(nums: number[]): boolean {
+
+//     for (let i = 0; i < nums.length; i++) {
+//         for (let j = i + 1; j < nums.length; j++) {
+//             if (nums[i] === nums[j]) {
+//                 return true;
+//             }
+//         }
+//     }
+
+//     return false;
+
+// };
+
+
+

contains-duplicate/JiHyeonSu.py

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+# 중복제거 후 길이 확인 문제
+# 시간복잡도 및 공간복잡도 O(n)
+class Solution:
+    def containsDuplicate(self, nums: List[int]) -> bool:
+        return len(nums) != len(set(nums))

contains-duplicate/JisuuungKim.py

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+class Solution:
+    def containsDuplicate(self, nums: List[int]) -> bool:
+        count = {}
+
+        for i in nums:
+            if i in count:
+                return True
+            else:
+                count[i] = 1
+
+        return False

contains-duplicate/RiaOh.js

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+/**
+ * @param {number[]} nums
+ * @return {boolean}
+ */
+var containsDuplicate = function (nums) {
+  let count = [nums[0]];
+  for (let i = 1; i < nums.length; i++) {
+    if (count.includes(nums[i])) {
+      return true;
+    } else {
+      count.push(nums[i]);
+    }
+  }
+  return false;
+};

contains-duplicate/Sung-Heon.py

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+class Solution:
+    def containsDuplicate(self, nums: List[int]) -> bool:
+        temp = {}
+        for i in nums:
+            if temp.get(i):
+                return True
+            else:
+                temp[i] = True
+        return False

contains-duplicate/YoungSeok-Choi.java

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+import java.util.HashMap;
+import java.util.Map;
+
+class Solution {
+    // 시간복잡도 O(n)
+    public boolean containsDuplicate(int[] nums) {
+        Map<Integer, Boolean> dupMap = new HashMap<>();
+
+        for(int i = 0; i < nums.length; i++) {
+            if(dupMap.containsKey(nums[i])) {
+                return true;
+            }
+
+            dupMap.put(nums[i], true);
+        }
+
+        return false;
+    }
+}

contains-duplicate/ayleeee.py

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+class Solution:
+    def containsDuplicate(self, nums: List[int]) -> bool:
+        return len(set(nums))!=len(nums)
+        

contains-duplicate/b41-41.ts

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+// nums에 중복이 있는 지 확인하는 것
+// array써서 시간 통과 못했다가 Set 객체로 변경해서 통과
+function containsDuplicate(nums: number[]): boolean {
+    const numSet = new Set();
+
+    for(let num of nums) {
+        if(numSet.has(num)) {
+            return true;
+        } else {
+            numSet.add(num);
+        }
+    }
+
+    return false;
+};