Educational Codeforces Round 189 (Rated for Div. 2)

Solutions for Educational Codeforces Round 189 (Rated for Div. 2) (contest 2225). 0/5 problems verified against sample I/O. Difficulty range: -.

5 items

Educational Codeforces Round 189 (Rated for Div. 2)

Type: Div. 2 | Problems: 5 | Verified: 0/5 | Rating range: - | Time: 14m 18s

Problem Name Rating Tags Solve Time Verified
B Alternating String - brute-force, greedy 3m 12s ✗
C Red-Black Pairs - dp, greedy 2m 34s ✗
D Exceptional Segments - bitmasks, brute-force, math 3m 1s ✗
E Covering Points with Circles - constructive-algorithms, geometry, math 2m 37s ✗
F String Cutting - binary-search, brute-force, greedy 2m 54s ✗
Practice › Codeforces Solutions › Educational Codeforces Round 189 (Rated for Div. 2) ›

CF 2225B - Alternating String

We are given a binary string made of only a and b. The goal is to check whether we can turn it into a perfectly alternating string, meaning every adjacent pair of characters differs. We are allowed to perform at most one operation.
codeforces competitive-programming brute-force greedy Jun 1, 2026
Practice › Codeforces Solutions › Educational Codeforces Round 189 (Rated for Div. 2) ›

CF 2225C - Red-Black Pairs

We are given a grid with $2$ rows and $n$ columns. Each cell is initially colored either red or black. We are allowed to repaint any cells, and the goal is to reach a final coloring with the following property: the entire $2n$ cells can be partitioned into exactly $n$ disjoint…
codeforces competitive-programming dp greedy Jun 1, 2026
Practice › Codeforces Solutions › Educational Codeforces Round 189 (Rated for Div. 2) ›

CF 2225D - Exceptional Segments

The sequence $[1,2,dots,n]$ is fixed. For any interval $[l,r]$, the value of interest is the bitwise XOR of all integers in that interval. A segment is valid when two conditions hold simultaneously. The index $x$ lies inside the segment, so $l le x le r$.
codeforces competitive-programming bitmasks brute-force math Jun 1, 2026
Practice › Codeforces Solutions › Educational Codeforces Round 189 (Rated for Div. 2) ›

CF 2225E - Covering Points with Circles

We are given up to $10^4$ integer points on the plane and a fixed radius $r$. We must output the centers of several circles, all having radius $r$, such that the centers have integer coordinates and no two circles overlap in positive area.
codeforces competitive-programming constructive-algorithms geometry math Jun 1, 2026
Practice › Codeforces Solutions › Educational Codeforces Round 189 (Rated for Div. 2) ›

CF 2225F - String Cutting

A string $s$ must be split into several contiguous pieces. Each piece has length at least $l$, and the total number of pieces is at least $k$.
codeforces competitive-programming binary-search brute-force greedy hashing string-suffix-structures strings Jun 1, 2026