UDESC Selection Contest 2023-2

15 problems from UDESC Selection Contest 2023-2 (contest 105055), difficulty -. 12/15 solutions verified against sample I/O.

15 items

UDESC Selection Contest 2023-2

Special | 15 problems | 12/15 verified | Difficulty - | 16m 53s

# Problem Rating Tags Accepted Time ✓
A Sticker Album 1m 36s ✓
B Bit Tennis 1m 9s ✓
C Traveling Debtor 1m 10s ✓
D Whose Turn Is It? 56s ✓
E Email 1m 9s ✓
F Festa Junina 1m 24s ✓
G Genie in the Lamp 31s ✓
H Hawarma 54s ✓
I DJ Interface 1m 24s
J Party Game 1m 53s
K Knock Code 31s
L Le Caf\u00e9 1m 10s ✓
M Dimly Lit 58s ✓
N Nim? 1m 15s ✓
O Another Trip 53s ✓
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CF 105055N - Nim?

We start with a pile that initially contains $A times B$ stones. Two players alternate moves, with Machado always starting. On each turn, the current player changes the pile size by either adding or removing a number of stones, subject to restrictions that differ per player.
codeforces competitive-programming Jun 28, 2026
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CF 105055M - Dimly Lit

We are given a one-dimensional street segment from position 0 to position N, together with a set of lampposts placed at fixed integer coordinates along this segment.
codeforces competitive-programming Jun 28, 2026
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CF 105055L - Le Café

We are given a multiset of sprinkle packages, where each package contains a fixed positive number of sprinkles and must be used entirely or not at all.
codeforces competitive-programming Jun 28, 2026
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CF 105055J - Party Game

We are given a small group of at most seven players, each owning a “die” described indirectly through a string of length $M$.
codeforces competitive-programming Jun 28, 2026
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CF 105055I - DJ Interface

A circular vinyl disc is drawn on a square screen. The disc is centered in the square from the origin-aligned view, with its visible region being the set of points inside a circle of diameter $D$. A user clicks at one point on the disc, drags to another point, and releases.
codeforces competitive-programming Jun 28, 2026
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CF 105055A - Sticker Album

We are given a line of sticker packs, each pack having a cost and a multiset of stickers it contains. Each sticker has an identifier from 1 to M, and the goal is to acquire at least one copy of every identifier in this range.
codeforces competitive-programming Jun 28, 2026
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CF 105055F - Festa Junina

We are asked to construct a sequence of exactly $N$ positive integers such that the sequence is strictly increasing, and among all such sequences we want the one with minimum total cost. The cost structure is the key part.
codeforces competitive-programming Jun 28, 2026
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CF 105055B - Bit Tennis

We start with a binary string that represents an integer. Two players alternate turns, and on each turn a player is allowed to extend the string by adding exactly one bit either to the left or to the right.
codeforces competitive-programming Jun 28, 2026
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CF 105055O - Another Trip

The situation is a simple road trip with a mistake in direction. Two distances are relevant: the first is how far the travelers went after taking the wrong direction, and the second is the remaining distance from their starting point to the destination along the correct route.
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CF 105055K - Knock Code

Each uppercase letter must be translated into its position inside the fixed 5 by 5 Knock Code matrix. Every letter is represented by a pair consisting of its row and column. The numbers themselves are encoded as consecutive asterisks, so row 3 becomes and column 5 becomes .
codeforces competitive-programming Jun 28, 2026
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CF 105055H - Hawarma

We are given an integer parameter $N$ and a rational function $$f(x) = frac{5xN^2}{x^2 + 3xN - 5N^2}.$$ The task is to find all real values $a$ such that plugging $a$ into the function returns the same value, meaning $f(a) = a$.
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CF 105055G - Genie in the Lamp

We are given a string of length $N$ consisting of three kinds of characters: fixed opening parentheses, fixed closing parentheses, and wildcard positions written as ?. Each wildcard can independently be replaced by either ( or ).
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CF 105055E - Email

We are given a string made only of the characters a and b. This string is not arbitrary: it is supposed to be an encoding of a binary password where each 0 was replaced by the block ab and each 1 was replaced by the block aba.
codeforces competitive-programming Jun 28, 2026
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CF 105055D - Whose Turn Is It?

Two athletes alternate doing fixed-size blocks of repetitions at a gym. Marcel always performs the first block, then Joãozão, then Marcel again, and so on. Each block contains exactly M repetitions.
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CF 105055C - Traveling Debtor

The problem gives an undirected, unweighted graph of cities connected by roads. Lex starts at city 1 and must reach city N. Some cities are marked as “debt cities”, meaning passing through them is undesirable. A path is evaluated in two stages.
codeforces competitive-programming Jun 28, 2026