Codeforces Round 1042 (Div. 3)

8 problems from Codeforces Round 1042 (Div. 3) (contest 2131), difficulty 800-2600. 3/8 solutions verified against sample I/O.

8 items

Codeforces Round 1042 (Div. 3)

Div. 3 | 8 problems | 3/8 verified | Difficulty 800-2600 | 14m 55s

# Problem Rating Tags Accepted Time ✓
A Lever 800 math 38,855 1m 37s ✓
B Alternating Series 800 constructive-algorithms, greedy, math 30,946 2m 48s ✓
C Make it Equal 1100 math, number-theory 21,611 1m 43s
D Arboris Contractio 1400 data-structures, graphs, greedy 14,316 1m 33s
E Adjacent XOR 1400 brute-force, greedy 17,108 1m 30s
F Unjust Binary Life 1900 binary-search, data-structures, greedy 4,719 1m 46s ✓
G Wafu! 2000 bitmasks, brute-force, data-structures 3,770 2m 17s
H Sea, You & copriMe 2600 brute-force, constructive-algorithms, graphs 884 1m 41s
Practice › Codeforces Solutions › Codeforces Round 1042 (Div. 3) ›

CF 2131G - Wafu!

We start with a finite set of distinct positive integers. A single move depends entirely on the current minimum element of the set.
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CF 2131H - Sea, You & copriMe

The problem gives us an array of integers, each between 1 and some upper bound $m$, and asks us to find four distinct indices $p, q, r, s$ such that the pair $(ap, aq)$ and the pair $(ar, as)$ are both coprime.
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CF 2131F - Unjust Binary Life

We are given two binary strings, a and b, each of length n. They define a virtual n × n grid where each cell (i, j) contains the value a[i] XOR b[j]. Yuri starts at the top-left cell (1,1) and can only move either right or down.
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CF 2131E - Adjacent XOR

We are given two arrays, a and b, both of length n. We can perform an operation on a at most once per index: for any index i from 1 to n-1, we can set a[i] to a[i] XOR a[i+1].
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CF 2131D - Arboris Contractio

We are given a tree, an undirected connected graph with no cycles. Kagari can perform an operation that "re-roots" a path: choose two vertices, remove the edges along the path connecting them, and then reconnect all vertices along that path directly to the starting vertex.
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CF 2131B - Alternating Series

We need to construct an integer array of length n with two properties. The first property says neighboring elements must always have opposite signs. Since their product must be negative, neither element can be zero, and the signs must alternate.
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CF 2131C - Make it Equal

We start with a multiset $S$ of size $n$ and we want to transform it into another multiset $T$ of the same size. The only allowed move takes one element $x$ from $S$, deletes it, and replaces it with either $x+k$ or $ The core question is whether repeated applications of these…
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CF 2131A - Lever

We are given two arrays of equal length, a and b, and a machine called The Lever that iterates a process in which it adjusts the elements of a toward the elements of b.
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