From 352700a5edc898d2e6d67344d4dfc9ed06195105 Mon Sep 17 00:00:00 2001
From: Won Joon Thomas Choi <113500771+724thomas@users.noreply.github.com>
Date: Mon, 28 Sep 2026 20:49:16 +0900
Subject: [PATCH 1/3] Create 169. Majority Element.py

---
 .../169. Majority Element.py"                         | 11 +++++++++++
 1 file changed, 11 insertions(+)
 create mode 100644 "leetcode3/\354\265\234\354\233\220\354\244\200/169. Majority Element.py"

diff --git "a/leetcode3/\354\265\234\354\233\220\354\244\200/169. Majority Element.py" "b/leetcode3/\354\265\234\354\233\220\354\244\200/169. Majority Element.py"
new file mode 100644
index 00000000..083b6137
--- /dev/null
+++ "b/leetcode3/\354\265\234\354\233\220\354\244\200/169. Majority Element.py"	
@@ -0,0 +1,11 @@
+class Solution:
+    def majorityElement(self, nums: list[int]) -> int:
+        n = len(nums)
+        majority = n/2
+
+        counter = Counter(nums)
+        for num, freq in counter.items():
+            if freq >= majority:
+                return num
+        
+        return -1

From 261b33ed30db82703fc374d15e5d2ab5d0004ef7 Mon Sep 17 00:00:00 2001
From: Won Joon Thomas Choi <113500771+724thomas@users.noreply.github.com>
Date: Tue, 29 Sep 2026 22:18:30 +0900
Subject: [PATCH 2/3] Create 242. Valid Anagram.py

---
 .../242. Valid Anagram.py"                           | 12 ++++++++++++
 1 file changed, 12 insertions(+)
 create mode 100644 "leetcode3/\354\265\234\354\233\220\354\244\200/242. Valid Anagram.py"

diff --git "a/leetcode3/\354\265\234\354\233\220\354\244\200/242. Valid Anagram.py" "b/leetcode3/\354\265\234\354\233\220\354\244\200/242. Valid Anagram.py"
new file mode 100644
index 00000000..a9f2ca06
--- /dev/null
+++ "b/leetcode3/\354\265\234\354\233\220\354\244\200/242. Valid Anagram.py"	
@@ -0,0 +1,12 @@
+class Solution:
+    def isAnagram(self, s: str, t: str) -> bool:
+        if len(t) != len(s):
+            return False
+            
+        counter1 = Counter(s)
+        counter2 = Counter(t)
+
+        for char1, freq in counter1.items():
+            if counter2[char1] != freq:
+                return False
+        return True

From 792379916aad17ff037bacbc8b89703b7a104edf Mon Sep 17 00:00:00 2001
From: Won Joon Thomas Choi <113500771+724thomas@users.noreply.github.com>
Date: Tue, 29 Sep 2026 22:20:42 +0900
Subject: [PATCH 3/3] Create 413. Arithmetic Slices.py

---
 .../413. Arithmetic Slices.py"                | 40 +++++++++++++++++++
 1 file changed, 40 insertions(+)
 create mode 100644 "leetcode3/\354\265\234\354\233\220\354\244\200/413. Arithmetic Slices.py"

diff --git "a/leetcode3/\354\265\234\354\233\220\354\244\200/413. Arithmetic Slices.py" "b/leetcode3/\354\265\234\354\233\220\354\244\200/413. Arithmetic Slices.py"
new file mode 100644
index 00000000..07fdf0e6
--- /dev/null
+++ "b/leetcode3/\354\265\234\354\233\220\354\244\200/413. Arithmetic Slices.py"	
@@ -0,0 +1,40 @@
+#
+
+'''
+1. 아이디어 :
+diff가 다를때마다 자른다.
+자른 길이를 재귀함수를 통해 경우의 수를 구한다
+
+2. 시간복잡도 :
+    O(n + n)
+
+3. 자료구조/알고리즘 :
+dfs
+
+'''
+class Solution:
+    def numberOfArithmeticSlices(self, nums: list[int]) -> int:
+        if len(nums) <3:
+            return 0
+
+        @cache
+        def calc(n):
+            return n // 3 if n <= 3 else n-2 + calc(n-1)
+        
+        ans = 0
+        prevs = [nums[0], nums[1]]
+        diff = nums[1] - nums[0]
+
+        for num in nums[2:]:
+            if num - prevs[-1] == diff:
+                prevs.append(num)
+
+            elif num - prevs[-1] != diff:
+                if len(prevs) >= 3:
+                    ans += calc(len(prevs))
+                
+                diff = num - prevs[-1]
+                prevs = [prevs[-1], num]
+        ans += calc(len(prevs))
+        return ans            
+