Educational Codeforces Round 123 (Rated for Div. 2)

Solutions for Educational Codeforces Round 123 (Rated for Div. 2) (contest 1644). 3/6 problems verified against sample I/O. Difficulty range: 800-2900.

6 items

Educational Codeforces Round 123 (Rated for Div. 2)

Type: Div. 2 | Problems: 6 | Verified: 3/6 | Rating range: 800-2900 | Time: 9m 48s

Problem	Name	Rating	Tags	Solve Time	Verified
A	Doors and Keys	800	implementation	1m 14s	✓
B	Anti-Fibonacci Permutation	800	brute-force, constructive-algorithms, implementation	1m 50s	✗
C	Increase Subarray Sums	1400	brute-force, dp, greedy	1m 44s	✓
D	Cross Coloring	1700	data-structures, implementation, math	1m 11s	✓
E	Expand the Path	1900	brute-force, combinatorics, data-structures	2m 37s	✗
F	Basis	2900	combinatorics, fft, math	1m 12s	✗

Practice › Codeforces Solutions › Educational Codeforces Round 123 (Rated for Div. 2) ›

CF 1644E - Expand the Path

We are given an $n times n$ grid, with a robot starting at the top-left corner $(1,1)$. The robot can move right (R) or down (D) and is provided a sequence $s$ of such moves. Each move in $s$ is guaranteed not to take the robot outside the grid.

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CF 1644F - Basis

We are asked to cover all possible arrays of length n whose elements range from 1 to k using a sequence of arrays, where each array in the sequence can "generate" others through two operations.

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CF 1644B - Anti-Fibonacci Permutation

We need to construct permutations of the numbers from 1 to n such that no element starting from the third position equals the sum of the previous two elements.

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CF 1644D - Cross Coloring

We are given a grid that starts completely uncolored, with $n$ rows and $m$ columns. We then apply a sequence of operations. Each operation selects a row and a column, and paints every cell in that row and that column with a chosen non-white color.

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CF 1644C - Increase Subarray Sums

We are given an array of integers and a number $x$. The task is to compute, for each possible $k$ from 0 to $n$, the maximum sum of a contiguous subarray if we are allowed to add $x$ to exactly $k$ elements in the array.

Practice › Codeforces Solutions › Educational Codeforces Round 123 (Rated for Div. 2) ›

CF 1644A - Doors and Keys

The problem describes a narrow hallway with three doors and three keys, each uniquely colored red, green, or blue. The knight starts at the left end of the hallway, and the princess waits at the far right.