Codeforces Round 657 (Div. 2)

5 problems from Codeforces Round 657 (Div. 2) (contest 1379), difficulty 1500-2800. 0/5 solutions verified against sample I/O.

5 items

Codeforces Round 657 (Div. 2)

Div. 2 | 5 problems | 0/5 verified | Difficulty 1500-2800 | 27m 51s

#	Problem	Rating	Tags	Accepted	Time
A	Acacius and String	1500	brute-force, implementation, strings	12,327	6m 47s
B	Dubious Cyrpto	1500	binary-search, brute-force, math	13,180	2m 14s
C	Choosing flowers	2000	binary-search, brute-force, data-structures	6,080	6m 47s
E	Inverse Genealogy	2800	constructive-algorithms, divide-and-conquer, dp	473	1m 20s
F2	Chess Strikes Back (hard version)	2800	data-structures, divide-and-conquer	580	10m 43s

Practice › Codeforces Solutions › Codeforces Round 657 (Div. 2) ›

CF 1379F2 - Chess Strikes Back (hard version)

We are working on a very large grid of size $2n times 2m$, but we only care about the white cells, those where the sum of coordinates is even. Among these white cells, some are dynamically toggled between available and unavailable across a sequence of updates.

Practice › Codeforces Solutions › Codeforces Round 657 (Div. 2) ›

CF 1379A - Acacius and String

We are given a short string consisting of lowercase letters and question marks. Each question mark can later be replaced by any lowercase letter. After replacements, we want to end up with a string that contains the fixed pattern "abacaba" as a substring exactly once.

Practice › Codeforces Solutions › Codeforces Round 657 (Div. 2) ›

CF 1379C - Choosing flowers

We are choosing exactly $n$ flowers from $m$ available types, where each type can be used an unlimited number of times. The value of picking flowers is not linear per flower, instead each type behaves like a diminishing reward stream.

Practice › Codeforces Solutions › Codeforces Round 657 (Div. 2) ›

CF 1379E - Inverse Genealogy

Let $Nge 1$ be fixed. An $m$-survivor is a positive integer all of whose prime factors exceed $m$. Let $$f(x,m)={nle x:text{$n$ is an $m$-survivor}},$$ and let $$fk(x,m)={nle x:text{$n$ is an $m$-survivor having exactly $k$ prime factors}},$$ where prime factors are counted…

Practice › Codeforces Solutions › Codeforces Round 657 (Div. 2) ›

CF 1379B - Dubious Cyrpto

The problem asks us to reverse-engineer a simple integer encoding scheme. Pasha encrypts a strictly positive integer $n$ using three numbers $a$, $b$, and $c$, all constrained to lie between two given bounds $l$ and $r$. The encryption formula is $m = n cdot a + b - c$.