Codeforces Beta Round 68

Solutions for Codeforces Beta Round 68 (contest 74). 4/5 problems verified against sample I/O. Difficulty range: 1000-2800.

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Codeforces Beta Round 68

Type: Beta | Problems: 5 | Verified: 4/5 | Rating range: 1000-2800 | Time: 22m 53s

Problem	Name	Rating	Tags	Solve Time	Verified
A	Room Leader	1000	implementation	1m 35s	✓
B	Train	1500	dp, games, greedy	2m 11s	✓
C	Chessboard Billiard	2100	dfs-and-similar, dsu, graphs	1m 36s	✓
D	Hanger	2400	data-structures	1m 7s	✓
E	Shift It!	2800	constructive-algorithms	16m 24s	✗

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CF 74A - Room Leader

We are given the scoreboard data for every participant in a Codeforces room. Each contestant has a handle, a number of successful hacks, a number of unsuccessful hacks, and the points earned from problems A through E.

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CF 74B - Train

The train has n wagons arranged in a line. The controller moves deterministically: every minute he walks one wagon in his current direction, and when he reaches either end he reverses direction. His path is completely fixed once we know the initial wagon and direction.

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CF 74C - Chessboard Billiard

We have an n × m chessboard. A billiard ball moves diagonally like a bishop, but unlike a bishop it reflects off the borders of the board. When it hits a vertical wall, the horizontal component of the direction flips. When it hits a horizontal wall, the vertical component flips.

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CF 74D - Hanger

We have a single row of hooks, numbered from 1 to n, which initially are all empty. Employees arrive and leave at specified times, and each arrival or departure is encoded by an employee ID: the first occurrence is an arrival, the second is the departure, and so on.

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CF 74E - Shift It!

We have a 6 × 6 board containing the characters 0-9 and A-Z, each appearing exactly once. The target configuration is fixed: characters must appear in row-major order. The only allowed moves are cyclic shifts of complete rows or complete columns.