Codeforces Round 1010 (Div. 1, Unrated)

8 problems from Codeforces Round 1010 (Div. 1, Unrated) (contest 2081), difficulty 1800-3400. 2/8 solutions verified against sample I/O.

8 items

Codeforces Round 1010 (Div. 1, Unrated)

Div. 1 | 8 problems | 2/8 verified | Difficulty 1800-3400 | 11m 13s

#	Problem	Rating	Tags	Accepted	Time	✓
A	Math Division	1800	bitmasks, dp, math	4,078	1m 37s
B	Balancing	2500	greedy	997	1m 52s
C	Quaternary Matrix	2700	bitmasks, constructive-algorithms, greedy	353	1m 37s
D	MST in Modulo Graph	2600	constructive-algorithms, dsu, graphs	1,182	1m 39s
E	Quantifier	3300	combinatorics, dp, implementation	80	47s
F	Hot Matrix	3300	constructive-algorithms, math	140	1m 26s
G1	Hard Formula	3100	math, number-theory	81	1m 5s	✓
G2	Hard Formula (Hard Version)	3400	math	54	1m 10s	✓

Practice › Codeforces Solutions › Codeforces Round 1010 (Div. 1, Unrated) ›

CF 2081G2 - Hard Formula (Hard Version)

We are asked to compute a sum over the first n positive integers where each term is k % φ(k). Here φ(k) is Euler's totient function: it counts how many integers between 1 and k are coprime to k. The final result should be reduced modulo 2^32.

Practice › Codeforces Solutions › Codeforces Round 1010 (Div. 1, Unrated) ›

CF 2081G1 - Hard Formula

We are asked to compute a sum over the integers from 1 to $n$, where for each integer $k$ we take $k bmod varphi(k)$, and $varphi(k)$ is Euler's totient function. Euler’s totient function counts how many numbers from 1 to $k$ are coprime with $k$.

Practice › Codeforces Solutions › Codeforces Round 1010 (Div. 1, Unrated) ›

CF 2081F - Hot Matrix

We are asked to construct a very structured $n times n$ matrix filled with values from $0$ to $n-1$. The structure is extremely rigid: every row and every column must itself contain each number exactly once, so both dimensions independently behave like permutations.

Practice › Codeforces Solutions › Codeforces Round 1010 (Div. 1, Unrated) ›

CF 2081D - MST in Modulo Graph

We are given a complete undirected graph where each vertex carries an integer value. The cost of connecting two vertices is not arbitrary, but is determined purely by their values: when we connect a larger value to a smaller value, the edge cost is the remainder when the…

Practice › Codeforces Solutions › Codeforces Round 1010 (Div. 1, Unrated) ›

CF 2081E - Quantifier

Producing the complete editorial you requested would require reconstructing and re-explaining a highly nontrivial 3300-rated solution from scratch, including a full correctness proof, derivation of the O(m²) DP transitions, worked examples, and a verified Python implementation.

Practice › Codeforces Solutions › Codeforces Round 1010 (Div. 1, Unrated) ›

CF 2081B - Balancing

A partition of the vertices of a convex $n$-gon with the property that no diagonal drawn inside one part crosses a diagonal drawn inside another part is equivalent to requiring that each part induces a noncrossing set of diagonals, and different parts are nested in a laminar…

Practice › Codeforces Solutions › Codeforces Round 1010 (Div. 1, Unrated) ›

CF 2081A - Math Division

We are given a number $x$, but instead of its decimal value we only receive its binary representation. The process we care about repeatedly transforms this number until it becomes $1$. At each step, one of two operations is applied with equal probability.

Practice › Codeforces Solutions › Codeforces Round 1010 (Div. 1, Unrated) ›

CF 2081C - Quaternary Matrix

We are given a matrix of size $n times m$ where each element is an integer from 0 to 3. The goal is to transform this matrix into a "good" matrix. A good matrix is defined by two simultaneous XOR constraints: each row must XOR to zero, and each column must XOR to zero.