21-froglike6

froglike6/README.md

@@ -22,4 +22,5 @@
  | 18차시 | 2025.07.03 | 자릿수를 이용한 다이나믹 프로그래밍 | [합 찾기](https://www.acmicpc.net/problem/7786)|https://github.com/AlgoLeadMe/AlgoLeadMe-13/pull/69|
  | 19차시 | 2025.07.04 | 애드 혹 | [서로소 그래프 게임](https://www.acmicpc.net/problem/34035)|https://github.com/AlgoLeadMe/AlgoLeadMe-13/pull/72|
  | 20차시 | 2025.07.09 | 조합론 | [암호 만들기](https://www.acmicpc.net/problem/1759)|https://github.com/AlgoLeadMe/AlgoLeadMe-13/pull/77|
+ | 21차시 | 2025.07.14 | 기하학 | [Cows](https://www.acmicpc.net/problem/6850)|https://github.com/AlgoLeadMe/AlgoLeadMe-13/pull/82|
  ---

froglike6/geometry/6850.py

@@ -0,0 +1,41 @@
+import sys
+input = sys.stdin.readline
+
+def cross(o, a, b):
+    return (a[0]-o[0])*(b[1]-o[1])-(a[1]-o[1])*(b[0]-o[0])
+
+def convex_hull(points):
+    points = sorted(set(points))
+
+    if len(points) <= 1:
+        return points
+
+    lower = []
+    for p in points:
+        while len(lower) >= 2 and cross(lower[-2], lower[-1], p) <= 0:
+            lower.pop()
+        lower.append(p)
+
+    upper = []
+    for p in reversed(points):
+        while len(upper) >= 2 and cross(upper[-2], upper[-1], p) <= 0:
+            upper.pop()
+        upper.append(p)
+
+    return lower[:-1] + upper[:-1]
+
+def shoelace_area(polygon):
+    n = len(polygon)
+    area = 0
+    for i in range(n):
+        x1, y1 = polygon[i]
+        x2, y2 = polygon[(i + 1) % n]
+        area += (x1 * y2) - (x2 * y1)
+    return abs(area) / 2
+
+input_points = []
+for _ in range(int(input())):
+    a, b = map(int,input().split())
+    input_points.append((a,b))
+
+print(int(shoelace_area(convex_hull(input_points))//50))