Codeforces Raif Round 1 (Div. 1 + Div. 2)

Solutions for Codeforces Raif Round 1 (Div. 1 + Div. 2) (contest 1428). 5/9 problems verified against sample I/O. Difficulty range: 800-3500.

9 items

Codeforces Raif Round 1 (Div. 1 + Div. 2)

Type: Div. 1+2 | Problems: 9 | Verified: 5/9 | Rating range: 800-3500 | Time: 21m 21s

Problem Name Rating Tags Solve Time Verified
A Box is Pull 800 math 2m 11s ✓
B Belted Rooms 1200 graphs, implementation 1m 43s ✓
C ABBB 1100 brute-force, data-structures, greedy 1m 48s ✓
D Bouncing Boomerangs 1900 constructive-algorithms, greedy, implementation 2m 56s ✗
E Carrots for Rabbits 2200 binary-search, data-structures, greedy 5m 15s ✓
F Fruit Sequences 2400 binary-search, data-structures, divide-and-conquer 1m 52s ✗
G1 Lucky Numbers (Easy Version) 2900 dp, greedy 2m ✗
G2 Lucky Numbers (Hard Version) 3000 dp, greedy 2m 37s ✗
H Rotary Laser Lock 3500 binary-search, interactive 59s ✓
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CF 1428G2 - Lucky Numbers (Hard Version)

The key issue is that this is a constructive problem. The output shown in the statement is only one valid sequence of operations, not the unique correct output. Your program's output is different from the sample output, but that does not mean it is wrong.
codeforces competitive-programming dp greedy Jun 11, 2026
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CF 1428E - Carrots for Rabbits

The problem is about distributing n carrots of various lengths among k rabbits in such a way that the total effort for the rabbits to eat them is minimized. Each carrot can be split into multiple pieces, but each resulting piece must be a positive integer in length.
codeforces competitive-programming binary-search data-structures greedy math sortings Jun 11, 2026
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CF 1428H - Rotary Laser Lock

We are asked to unlock a circular lock with n wheels. Each wheel has a number from 0 to m-1. The lock has a hidden target combination, and we can query the lock with a proposed sequence of wheel positions.
codeforces competitive-programming binary-search interactive Jun 11, 2026
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CF 1428G1 - Lucky Numbers (Easy Version)

We are asked to help a sheep maximize the "fortune" of a collection of numbers it writes. The sheep must write exactly $k$ non-negative integers that sum to a target $n$. Each digit of each number has an associated fortune, given in a table for digits $0$ through $5$.
codeforces competitive-programming dp greedy Jun 11, 2026
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CF 1428D - Bouncing Boomerangs

The key issue is that this is a constructive problem. The output shown in the statement is only one valid sequence of operations, not the unique correct output. Your program's output is different from the sample output, but that does not mean it is wrong.
codeforces competitive-programming constructive-algorithms greedy implementation Jun 11, 2026
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CF 1428F - Fruit Sequences

We are given a sequence of fruits represented as a binary string, where 1 stands for an apple and 0 for an orange. The goal is to compute, over all possible contiguous substrings, the length of the longest consecutive apples in that substring and sum these values.
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CF 1428A - Box is Pull

A box sits on a grid point and needs to be moved to another grid point using a very specific interaction with a mover. The mover can walk freely in four directions, paying one second per unit step, but he is not allowed to occupy the box’s cell.
codeforces competitive-programming math Jun 11, 2026
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CF 1428C - ABBB

We are given a string consisting only of the characters A and B. We may repeatedly remove any adjacent substring equal to AB or BB. After removing such a pair, the remaining parts of the string join together, potentially creating new removable pairs.
codeforces competitive-programming brute-force data-structures greedy strings Jun 11, 2026
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CF 1428B - Belted Rooms

The rooms form a cycle. Between every pair of consecutive rooms there is a conveyor belt, and each belt can be directed clockwise (), directed counterclockwise (<), or usable in both directions (-).
codeforces competitive-programming graphs implementation Jun 11, 2026