Educational Codeforces Round 49 (Rated for Div. 2)

7 problems from Educational Codeforces Round 49 (Rated for Div. 2) (contest 1027), difficulty 1000-2600. 4/7 solutions verified against sample I/O.

7 items

Educational Codeforces Round 49 (Rated for Div. 2)

Div. 2 | 7 problems | 4/7 verified | Difficulty 1000-2600 | 35m 5s

#	Problem	Rating	Tags	Accepted	Time	✓
A	Palindromic Twist	1000	implementation, strings	18,799	6m 17s	✓
B	Numbers on the Chessboard	1200	implementation, math	8,744	3m 37s
C	Minimum Value Rectangle	1600	greedy	7,152	6m 46s
D	Mouse Hunt	1700	dfs-and-similar, graphs	8,366	3m 49s	✓
E	Inverse Coloring	2100	combinatorics, dp, math	2,362	2m 36s	✓
F	Session in BSU	2400	binary-search, dfs-and-similar, dsu	1,947	6m 57s
G	X-mouse in the Campus	2600	bitmasks, math, number-theory	360	5m 3s	✓

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CF 1027F - Session in BSU

We are given a collection of tasks, each task representing an exam that must be scheduled on exactly one of two possible days. For exam $i$, there are two candidate days $ai$ and $bi$, and we must choose one of them.

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CF 1027G - X-mouse in the Campus

We are given a system of rooms labeled from 0 to $m-1$. A token, called the x-mouse, starts in an unknown room and evolves deterministically: if it is in room $i$, after one second it moves to $i cdot x bmod m$.

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CF 1027E - Inverse Coloring

We are counting binary matrices of size $n times n$, where each cell is either black or white, but with two structural restrictions. The first restriction is a strong symmetry condition called “beauty”.

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CF 1027D - Mouse Hunt

We can think of the dorm as a directed graph where each room has exactly one outgoing edge. From every room i, the mouse deterministically moves to a[i] after one second.

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CF 1027C - Minimum Value Rectangle

We are given several independent sets of stick lengths. For each set, we need to pick exactly four sticks such that they form a rectangle, meaning we need two equal pairs of lengths: one pair for the height and one pair for the width.

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CF 1027A - Palindromic Twist

We are given several independent strings. Each string has even length, and every character is a lowercase English letter. For each character, we are forced to modify it exactly once, and the modification rule is fixed: we can only move one step in the alphabet either down or up.

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CF 1027B - Numbers on the Chessboard

We are working with an $n times n$ grid whose cells are filled with the numbers from $1$ to $n^2$, but not in a simple linear order. Instead, the grid is split into two disjoint groups of cells based on the parity of the sum of coordinates.