From e9f8a75be620650f07e830b192103c5d9c4b4924 Mon Sep 17 00:00:00 2001
From: sejineer <jinpark99@nave.com>
Date: Thu, 1 May 2025 04:27:28 +0900
Subject: [PATCH 1/5] best-time-to-buy-and-sell-stock solution

---
 best-time-to-buy-and-sell-stock/sejineer.py | 15 +++++++++++++++
 1 file changed, 15 insertions(+)
 create mode 100644 best-time-to-buy-and-sell-stock/sejineer.py

diff --git a/best-time-to-buy-and-sell-stock/sejineer.py b/best-time-to-buy-and-sell-stock/sejineer.py
new file mode 100644
index 000000000..fd9907f4f
--- /dev/null
+++ b/best-time-to-buy-and-sell-stock/sejineer.py
@@ -0,0 +1,15 @@
+"""
+시간 복잡도: O(N)
+공간 복잡도: O(1)
+"""
+class Solution:
+    def maxProfit(self, prices: List[int]) -> int:
+        buy = prices[0]
+        result = 0
+        
+        for price in prices:
+            profit = price - buy
+            buy = min(buy, price)
+            result = max(profit, result)
+        
+        return result

From bff5b2f010dc44a898b7962c4a3a1a4b20f76615 Mon Sep 17 00:00:00 2001
From: sejineer <jinpark99@nave.com>
Date: Thu, 1 May 2025 10:29:11 +0900
Subject: [PATCH 2/5] group-anagrams solution

---
 group-anagrams/sejineer.py | 14 ++++++++++++++
 1 file changed, 14 insertions(+)
 create mode 100644 group-anagrams/sejineer.py

diff --git a/group-anagrams/sejineer.py b/group-anagrams/sejineer.py
new file mode 100644
index 000000000..426282568
--- /dev/null
+++ b/group-anagrams/sejineer.py
@@ -0,0 +1,14 @@
+"""
+시간 복잡도: O(N * K) N=문자열 개수, 평균 문자열 길이 = K (최대 100)
+공간 복잡도: O(N * K) 
+"""
+from collections import Counter, defaultdict
+
+class Solution:
+    def groupAnagrams(self, strs: List[str]) -> List[List[str]]:
+        strs_dict = defaultdict(list)
+        for s in strs:
+            s_counter = Counter(s)
+            strs_dict[frozenset(s_counter.items())].append(s)
+        
+        return list(strs_dict.values())

From 280072846ad8f81e29a2af03ce49a3d1d91c7dd7 Mon Sep 17 00:00:00 2001
From: sejineer <jinpark99@nave.com>
Date: Thu, 1 May 2025 18:37:54 +0900
Subject: [PATCH 3/5] word-break solution

---
 word-break/sejineer.py | 14 ++++++++++++++
 1 file changed, 14 insertions(+)
 create mode 100644 word-break/sejineer.py

diff --git a/word-break/sejineer.py b/word-break/sejineer.py
new file mode 100644
index 000000000..9029ba50e
--- /dev/null
+++ b/word-break/sejineer.py
@@ -0,0 +1,14 @@
+class Solution:
+    def wordBreak(self, s: str, wordDict: List[str]) -> bool:
+        
+        @cache
+        def dfs(k: int) -> bool:
+            if k == len(s):
+                return True
+            for word in wordDict:
+                if s[k : k + len(word)] == word:
+                    if dfs(k + len(word)):
+                        return True
+            return False
+        
+        return dfs(0)

From 62bf33503656c8e8c8552ab34c584f2d2cc379ec Mon Sep 17 00:00:00 2001
From: sejineer <jinpark99@nave.com>
Date: Thu, 1 May 2025 18:54:39 +0900
Subject: [PATCH 4/5] word-break add comment

---
 word-break/sejineer.py | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/word-break/sejineer.py b/word-break/sejineer.py
index 9029ba50e..380a8a76a 100644
--- a/word-break/sejineer.py
+++ b/word-break/sejineer.py
@@ -1,3 +1,7 @@
+"""
+시간 복잡도: O(n * D * L) n = 문자열 길이, D = 사전 크기, L = 단어 평균 길이
+공간 복잡도: O(n)
+"""
 class Solution:
     def wordBreak(self, s: str, wordDict: List[str]) -> bool:
         

From c51b8bdce18a5f59ed00ce01003ca1c206895023 Mon Sep 17 00:00:00 2001
From: sejineer <jinpark99@nave.com>
Date: Fri, 2 May 2025 01:06:44 +0900
Subject: [PATCH 5/5] implement-trie-prefix-tree solution

---
 implement-trie-prefix-tree/sejineer.py | 29 ++++++++++++++++++++++++++
 1 file changed, 29 insertions(+)
 create mode 100644 implement-trie-prefix-tree/sejineer.py

diff --git a/implement-trie-prefix-tree/sejineer.py b/implement-trie-prefix-tree/sejineer.py
new file mode 100644
index 000000000..d4de97b75
--- /dev/null
+++ b/implement-trie-prefix-tree/sejineer.py
@@ -0,0 +1,29 @@
+class Trie:
+
+    def __init__(self):
+        self.root = {"$": True}        
+
+    def insert(self, word: str) -> None:
+        node = self.root
+        for ch in word:
+            if ch not in node:
+                node[ch] = {"$": False}
+            node = node[ch]
+        node["$"] = True
+
+
+    def search(self, word: str) -> bool:
+        node = self.root
+        for ch in word:
+            if ch not in node:
+                return False
+            node = node[ch]
+        return node["$"]
+
+    def startsWith(self, prefix: str) -> bool:
+        node = self.root
+        for ch in prefix:
+            if ch not in node:
+                return False
+            node = node[ch]
+        return True