[hu6r1s] WEEK 05 Solutions

best-time-to-buy-and-sell-stock/hu6r1s.py

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+class Solution:
+    """
+    1. 브루트포스
+    2중 for문이라서 O(n^2)임.
+    prices의 길이가 10^5이므로 10^10이 되면서 시간초과가 발생
+
+    2. 이분탐색으로 가능할까 했지만 DP를 사용해야 하는 문제 같음
+    시간복잡도는 O(n)이 나옴
+    """
+    """
+    def maxProfit(self, prices: List[int]) -> int:
+        max_profit = 0
+        for i in range(len(prices)-1):
+            for j in range(i, len(prices)):
+                profit = prices[j] - prices[i]
+                max_profit = max(max_profit, profit)
+        return max_profit
+    """
+    def maxProfit(self, prices: List[int]) -> int:
+        max_profit = 0
+        min_price = prices[0]
+        for price in prices:
+            max_profit = max(max_profit, price - min_price)
+            min_price = min(price, min_price)
+        return max_profit

encode-and-decode-strings/hu6r1s.py

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+class Solution:
+    """
+    @param: strs: a list of strings
+    @return: encodes a list of strings to a single string.
+    """
+    def encode(self, strs):
+        return "secretKey!@#".join(strs)
+
+    """
+    @param: str: A string
+    @return: decodes a single string to a list of strings
+    """
+    def decode(self, str):
+        return str.split("secretKey!@#")

group-anagrams/hu6r1s.py

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+from collections import defaultdict
+
+class Solution:
+    """
+    1. 정렬된 값이 딕셔너리에 있으면 리스트 형식으로 삽입
+    """
+    def groupAnagrams(self, strs: List[str]) -> List[List[str]]:
+        dict_strs = defaultdict(list)
+
+        for word in strs:
+            dict_strs[str(sorted(word))].append(word)
+        return list(dict_strs.values())