Educational Codeforces Round 180 (Rated for Div. 2)

6 problems from Educational Codeforces Round 180 (Rated for Div. 2) (contest 2112), difficulty 800-2800. 2/6 solutions verified against sample I/O.

6 items

Educational Codeforces Round 180 (Rated for Div. 2)

Div. 2 | 6 problems | 2/6 verified | Difficulty 800-2800 | 9m 9s

#	Problem	Rating	Tags	Accepted	Time	✓
A	Race	800	implementation, math	29,252	1m 18s	✓
B	Shrinking Array	1100	brute-force, greedy	21,107	1m 11s	✓
C	Coloring Game	1300	binary-search, brute-force, greedy	17,712	1m 50s
D	Reachability and Tree	1700	constructive-algorithms, dfs-and-similar, graphs	9,439	1m 29s
E	Tree Colorings	2200	combinatorics, dfs-and-similar, dp	3,378	1m 40s
F	Variables and Operations	2800	graphs, greedy, shortest-paths	637	1m 41s

Practice › Codeforces Solutions › Educational Codeforces Round 180 (Rated for Div. 2) ›

CF 2112F - Variables and Operations

We are given a directed system of value propagation rules over $n$ variables. Each rule says that one variable $x$ can potentially be reduced using the value of another variable $y$, shifted by a constant $z$, through an operation of the form $ax leftarrow min(ax, ay + z)$.

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CF 2112E - Tree Colorings

We are given a rooted tree, and every vertex must be assigned one of three colors: green, blue, or yellow. The root is fixed to be green. A coloring is considered valid when two connectivity constraints hold.

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CF 2112D - Reachability and Tree

We are asked to take an undirected tree and assign a direction to each edge so that the number of ordered vertex pairs $(u, v)$ where there is a directed path from $u$ to $v$ equals exactly $n$, the number of vertices.

Practice › Codeforces Solutions › Educational Codeforces Round 180 (Rated for Div. 2) ›

CF 2112C - Coloring Game

We are given a sorted array of integers, and we need to count how many ways Alice can pick exactly three distinct indices such that no matter what Bob does afterward, Alice’s chosen triple is “safe”. The sequence of events matters. Alice first selects three elements.

Practice › Codeforces Solutions › Educational Codeforces Round 180 (Rated for Div. 2) ›

CF 2112A - Race

In this problem, Alice and Bob are racing to a prize that will appear at one of two distinct points on a one-dimensional line. Alice has already chosen her starting point a.

Practice › Codeforces Solutions › Educational Codeforces Round 180 (Rated for Div. 2) ›

CF 2112B - Shrinking Array

We are given an array of integers, and we want to make it "beautiful." A beautiful array has at least two elements and contains at least one pair of adjacent elements whose difference is at most one.