[최원준] 2026/10/06

leetcode3/최원준/125. Valid Palindrome.py

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+#
+
+'''
+1. 아이디어 :
+
+
+2. 시간복잡도 :
+    O(n)
+
+3. 자료구조/알고리즘 :
+
+
+'''
+class Solution:
+    def isPalindrome(self, s: str) -> bool:
+        ans = ""
+        for c in s:
+            if c.isalpha() or c.isnumeric():
+                ans += c
+        return ans.lower() == ans[::-1].lower()

leetcode3/최원준/447. Number of Boomerangs.py

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+#
+
+'''
+1. 아이디어 :
+기준 포인트와 나머지 포인트들의 거리를 구하고 카운트를 한다.
+카운트된 갯수(m)중 2개씩 조합한다 m * (m-1)
+
+2. 시간복잡도 :
+    O(n * n)
+
+3. 자료구조/알고리즘 :
+hashmap
+
+'''
+class Solution:
+    def numberOfBoomerangs(self, points: list[list[int]]) -> int:
+
+        def get_distance(p1, p2):
+            x1, y1 = p1
+            x2, y2 = p2
+            return (x1-x2)**2 + abs(y1-y2)**2
+
+        n = len(points)
+        # distances = [[0 for _ in range(n)] for _ in range(n)]
+
+        # for row in range(n):
+        #     for col in range(n):
+        #         if row == col: continue
+        #         distances[row][col] = get_distance(points[row], points[col])
+
+        # for a in distances:
+        #     print(a)
+
+        ans = 0
+        for mid in points:
+            distances = defaultdict(int)
+
+            for point in points:
+                if mid == point:
+                    continue
+
+                distance = get_distance(mid, point)
+                distances[distance] += 1
+
+            for _, count in distances.items():
+                ans += count * (count-1)
+        return ans