UBC Summer Contest 2018

8 problems from UBC Summer Contest 2018 (contest 102319), difficulty -. 8/8 solutions verified against sample I/O.

8 items

UBC Summer Contest 2018

Special | 8 problems | 8/8 verified | Difficulty - | 55m 44s

# Problem Rating Tags Accepted Time ✓
A Andrew and Efficient Change 2m 41s ✓
B Paul's Badminton 3m 43s ✓
C Cyclic Song 9m 4s ✓
D David vs David 10m 25s ✓
E Enegue's Enigmatic Lanterns 12m 47s ✓
F Forever Young 2m 3s ✓
G Jonathan and Jason at the Jowling Jalley I 7m 57s ✓
Q Quirky Queries 7m 4s ✓
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CF 102319F - Forever Young

The students have distinct ages, so an arrangement of the class is simply a permutation of the numbers (1,ldots,s). Henry's maximum number of circled students is the length of the longest increasing subsequence of that permutation.
codeforces competitive-programming Aug 14, 2026
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CF 102319A - Andrew and Efficient Change

We have a coin system containing n distinct denominations, including denomination 1. Andrew must pay separately for every amount in the consecutive interval [l, r]. For each amount, he wants the minimum possible number of coins whose values sum exactly to that amount.
codeforces competitive-programming Aug 14, 2026
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CF 102319B - Paul's Badminton

The roads form a tree, so between any two places there is exactly one route. An employee assigned to go from a to b uses every edge on that unique path on every day from s through t. Paul pays once for an edge on a given day, regardless of how many employees use that edge.
codeforces competitive-programming Aug 14, 2026
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CF 102319E - Enegue's Enigmatic Lanterns

We have a row of n lanterns, exactly k of them are on, and 4 <= k <= n <= 100. We can ask the judge about any subset of lanterns. If that subset contains x lit lanterns, the judge does not reveal x. Instead, it returns the number of divisors of x that are composite.
codeforces competitive-programming Aug 14, 2026
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CF 102319C - Cyclic Song

A valid Type (N) song is exactly a binary de Bruijn cycle of order (N). Its period has length (2^N), and every binary string of length (N) appears exactly once during one period. The input gives (N), followed by two length-(N) strings (S) and (T).
codeforces competitive-programming Aug 14, 2026
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CF 102319Q - Quirky Queries

We maintain an array of quirky integers. A quirky integer is square-free, and every prime factor is below 300. There are only 62 such primes, so every value can be represented by a 62-bit mask telling us which primes occur in its factorization.
codeforces competitive-programming Aug 13, 2026
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CF 102319G - Jonathan and Jason at the Jowling Jalley I

We have a triangular arrangement of pins with n pins on the bottom row, n - 1 on the row above it, and so on, for a total of [ 1+2+dots+n=frac{n(n+1)}2 ] pins. After the ball is rolled, the only pin that the ball itself can knock down is the top pin.
codeforces competitive-programming Aug 13, 2026
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CF 102319D - David vs David

We have a two-pile impartial game. A position is represented by the two pile sizes, say (x, y). On a turn, a player may remove any positive number of stones from exactly one pile.
codeforces competitive-programming Aug 13, 2026