Codeforces Round 889 (Div. 2)

Solutions for Codeforces Round 889 (Div. 2) (contest 1855). 1/7 problems verified against sample I/O. Difficulty range: 800-3000.

7 items

Codeforces Round 889 (Div. 2)

Type: Div. 2 | Problems: 7 | Verified: 1/7 | Rating range: 800-3000 | Time: 12m 17s

Problem	Name	Rating	Tags	Solve Time	Verified
A	Dalton the Teacher	800	greedy, math	1m 49s	✗
B	Longest Divisors Interval	900	brute-force, combinatorics, greedy	1m 18s	✓
C1	Dual (Easy Version)	1400	constructive-algorithms	2m 23s	✗
C2	Dual (Hard Version)	1900	constructive-algorithms, math	1m 58s	✗
D	Earn or Unlock	2200	bitmasks, brute-force, dp	1m 42s	✗
E	Expected Destruction	2500	dp, math, probabilities	1m 43s	✗
F	Michael and Hotel	3000	binary-search, interactive	1m 24s	✗

Practice › Codeforces Solutions › Codeforces Round 889 (Div. 2) ›

CF 1855F - Michael and Hotel

We are given a hotel with n rooms, numbered 1 through n, each equipped with a teleporter that deterministically sends anyone in that room to a fixed target room.

Practice › Codeforces Solutions › Codeforces Round 889 (Div. 2) ›

CF 1855E - Expected Destruction

We are given a set of distinct integers between 1 and some maximum value m. At each second, we remove a random element x from the set. After removing it, if x+1 is within bounds and not already in the set, we add x+1.

Practice › Codeforces Solutions › Codeforces Round 889 (Div. 2) ›

CF 1855D - Earn or Unlock

We are given a sequence of cards arranged in a line. Each card has a numeric value and starts either locked or unlocked depending on its position: initially only the first card can be used, while all others become usable only after being unlocked through earlier actions.

Practice › Codeforces Solutions › Codeforces Round 889 (Div. 2) ›

CF 1855C2 - Dual (Hard Version)

We are given an array of integers, which can be positive, negative, or zero, and the task is to transform this array into a non-decreasing sequence. The only allowed operation is to pick two indices $i$ and $j$ and add the value at $aj$ to $ai$.

Practice › Codeforces Solutions › Codeforces Round 889 (Div. 2) ›

CF 1855C1 - Dual (Easy Version)

We are allowed to repeatedly pick two positions in an array and add the value of one position into another. The source element is not consumed or changed when it is used, so the operation behaves like a reusable “transfer of value” between indices.

Practice › Codeforces Solutions › Codeforces Round 889 (Div. 2) ›

CF 1855A - Dalton the Teacher

The problem asks us to make every student in a classroom "happy" by ensuring that no student sits on a chair with the same number as their own. We are given an initial permutation of students to chairs.

Practice › Codeforces Solutions › Codeforces Round 889 (Div. 2) ›

CF 1855B - Longest Divisors Interval

We are asked to work with a positive integer $n$ and find the longest contiguous range of positive integers $[l, r]$ such that each number in this interval divides $n$. In other words, for every integer $i$ between $l$ and $r$, $n bmod i = 0$.