2026 ICPC Asia Pacific Championship - Online Mirror (Unrated, Online Mirror, ICPC Rules, Teams Preferred)

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2206 2026 ICPC Asia Pacific Championship - Online Mirror (Unrated, Online Mirror, ICPC Rules, Teams Preferred) FINISHED False 18000 3471323 March 8, 2026, 1:45 a.m.

Problems

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( 31 ) L Onion PROGRAMMING

Onions are widely used in cuisines around the world. This problem is about an "onion peeling" process in geometry. A set of points in a two-dimensional plane is convex if, for any pair of points (p) and (q) in the set, the line segment connecting (p) and (q) is entirely contained in the set. For a set of points (S), its convex hull is the smallest convex set containing all points in (S). You are given four integers (n), (a), (b), and (k). You have a set (S) of (n) points, initialized as follows: () S = \{ (x, (ax + b) \bmod n) \mid x = 0, 1, \ldots, n-1 \}. () You apply the following operation (k) times: let (H) be the convex hull of the set (S), and then remove from (S) all points that lie on the boundary of the convex hull (H). Note that (S) can become empty. In that case, its convex hull is also empty, and its area is zero. For each operation, determine the doubled area of the convex hull (H). It can be shown that this value is always an integer. The input consists of a single line containing four integers (n), (a), (b), and (k) ((1 \le n \le 10^9); (0 \le a, b \lt n); (1 \le k \le 300)). Output (k) lines. The (i)-th line should contain an integer representing the doubled area of the convex hull in the (i)-th operation. Explanation for the sample input/output #1 Figure L.1 illustrates the points in (S) and the boundary of the convex hull in the first operation. The area of the convex hull is (4), and thus the doubled area is (8). Explanation for the sample input/output #2 Figure L.2 illustrates the boundaries in the first four operations. The set (S) becomes empty after the fourth operation. The area for the fifth operation is (0).

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Tutorial (PDF)

Submissions

Submission Id
Author(s)
Index
Submitted
Verdict
Language
Test Set
Tests Passed
Time taken (ms)
Memory Consumed (bytes)
Tags
Rating
365822059 pyqjw1 L March 8, 2026, 8:33 a.m. OK C++20 (GCC 13-64) TESTS 150 62 102400
365826069 sanjoy_doit028 L March 8, 2026, 9:12 a.m. OK C++20 (GCC 13-64) TESTS 150 5578 5427200
365809540 hoangletuan L March 8, 2026, 6:21 a.m. OK C++20 (GCC 13-64) TESTS 150 6500 7987200
365836416 hpqclab L March 8, 2026, 10:54 a.m. OK C++23 (GCC 14-64, msys2) TESTS 150 2984 13209600
365820084 Momotaros L March 8, 2026, 8:10 a.m. OK C++23 (GCC 14-64, msys2) TESTS 150 5109 5632000
365852362 Quest1_2_3 L March 8, 2026, 1:33 p.m. OK C++23 (GCC 14-64, msys2) TESTS 150 6828 5529600
365849245 Ibrohim-Shamsiev L March 8, 2026, 1:04 p.m. OK C++23 (GCC 14-64, msys2) TESTS 150 7609 7168000
365842984 Kaling L March 8, 2026, noon OK C++23 (GCC 14-64, msys2) TESTS 150 9375 87961600
365856421 L March 8, 2026, 1:52 p.m. OK Unknown TESTS 0 0 0

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