Educational Codeforces Round 165 (Rated for Div. 2)

Solutions for Educational Codeforces Round 165 (Rated for Div. 2) (contest 1969). 3/6 problems verified against sample I/O. Difficulty range: 800-3000.

6 items

Educational Codeforces Round 165 (Rated for Div. 2)

Type: Div. 2 | Problems: 6 | Verified: 3/6 | Rating range: 800-3000 | Time: 13m 58s

Problem Name Rating Tags Solve Time Verified
A Two Friends 800 constructive-algorithms, implementation, math 1m 23s ✓
B Shifts and Sorting 1000 constructive-algorithms, greedy 5m 20s ✗
C Minimizing the Sum 1700 dp, implementation 2m 12s ✓
D Shop Game 1900 data-structures, greedy, math 1m 42s ✗
E Unique Array 2400 binary-search, data-structures, divide-and-conquer 1m 34s ✗
F Card Pairing 3000 dp, greedy, hashing 1m 47s ✓
Practice › Codeforces Solutions › Educational Codeforces Round 165 (Rated for Div. 2) ›

CF 1969B - Shifts and Sorting

We are given a binary string and allowed to repeatedly “rotate” any chosen contiguous segment. A rotation moves the last character of the chosen segment to its front, shifting the rest right by one position. Each such operation costs exactly the length of the chosen segment.
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Practice › Codeforces Solutions › Educational Codeforces Round 165 (Rated for Div. 2) ›

CF 1969F - Card Pairing

We are given a sequence of cards arranged in a fixed order, each card having a type from a range of $k$ labels. The process starts by taking the first $k$ cards into our hand.
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CF 1969E - Unique Array

We are given an array of integers and allowed to change elements arbitrarily, paying one unit cost per change. The goal is to modify the array so that every contiguous subarray contains at least one value that appears exactly once inside that subarray.
codeforces competitive-programming binary-search data-structures divide-and-conquer dp greedy Jun 8, 2026
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CF 1969D - Shop Game

We are given a collection of items, each item has two values. The first value represents how much Alice must pay to acquire the item, and the second value represents how much Bob would pay Alice for that item if it is not taken for free.
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CF 1969C - Minimizing the Sum

We are given an array of integers, and we are allowed to perform a limited number of operations. Each operation picks one position and overwrites its value with the value of one of its immediate neighbors.
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CF 1969A - Two Friends

Each friend is assigned exactly one other friend as their “best friend”, and this assignment forms a permutation of size $n$. The key rule is that a friend only attends the party if both they and their assigned best friend are invited.
codeforces competitive-programming constructive-algorithms implementation math Jun 8, 2026