think-cell Round 1

Solutions for think-cell Round 1 (contest 1930). 5/10 problems verified against sample I/O. Difficulty range: 800-3500.

10 items

think-cell Round 1

Type: Special | Problems: 10 | Verified: 5/10 | Rating range: 800-3500 | Time: 21m 36s

Problem Name Rating Tags Solve Time Verified
A Maximise The Score 800 greedy, sortings 1m 32s ✓
B Permutation Printing 1000 brute-force, constructive-algorithms, math 2m 25s ✓
C Lexicographically Largest 1700 binary-search, constructive-algorithms, data-structures 1m 46s ✗
D1 Sum over all Substrings (Easy Version) 1800 brute-force, dp, greedy 2m 11s ✗
D2 Sum over all Substrings (Hard Version) 2100 bitmasks, divide-and-conquer, dp 2m 36s ✓
E 2..3...4.... Wonderful! Wonderful! 2400 combinatorics, dp, math 1m 50s ✓
F Maximize the Difference 2700 bitmasks, brute-force, dfs-and-similar 2m 28s ✗
G Prefix Max Set Counting 3100 data-structures, dp, trees 1m 42s ✗
H Interactive Mex Tree 3300 constructive-algorithms, dfs-and-similar, interactive 3m 43s ✗
I Counting Is Fun 3500 combinatorics 1m 23s ✓
Practice › Codeforces Solutions › think-cell Round 1 ›

CF 1930H - Interactive Mex Tree

We are dealing with a tree, but the real structure we care about is hidden behind an interactive layer. In every test case, we must output two permutations of node labels.
codeforces competitive-programming constructive-algorithms dfs-and-similar interactive trees Jun 9, 2026
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CF 1930F - Maximize the Difference

We build an array incrementally. After every insertion we must compute $$f(a)=maxx left(maxi(aimid x)-mini(aimid x)right).$$ The value inserted at each step is encrypted by the previous answer, so the queries must be processed online.
codeforces competitive-programming bitmasks brute-force dfs-and-similar Jun 9, 2026
Practice › Codeforces Solutions › think-cell Round 1 ›

CF 1930G - Prefix Max Set Counting

We are asked to count the number of distinct prefix maximum sequences that can appear over all valid pre-order traversals of a rooted tree.
codeforces competitive-programming data-structures dp trees Jun 9, 2026
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CF 1930B - Permutation Printing

We are asked to construct a permutation of numbers from 1 to n such that a specific forbidden pattern never appears. The pattern involves two different starting positions i and j.
codeforces competitive-programming brute-force constructive-algorithms math Jun 9, 2026
Practice › Codeforces Solutions › think-cell Round 1 ›

CF 1930D1 - Sum over all Substrings (Easy Version)

We are given a binary string, and for each of its substrings, we want to compute the minimum number of ones required to form a “good” string with respect to that substring.
codeforces competitive-programming brute-force dp greedy strings Jun 9, 2026
Practice › Codeforces Solutions › think-cell Round 1 ›

CF 1930C - Lexicographically Largest

We are given an array a of length n. The task is to repeatedly select an element from a, add its value plus its current index to a set S, remove it from the array, and continue until a is empty. After all insertions, we sort the set S in decreasing order to form array b.
codeforces competitive-programming binary-search constructive-algorithms data-structures greedy sortings Jun 9, 2026
Practice › Codeforces Solutions › think-cell Round 1 ›

CF 1930I - Counting Is Fun

We are given a binary template string $p$ of length $n$. We are asked to count how many binary strings $q$ of the same length are valid under a global consistency rule that is defined locally in a slightly indirect way.
codeforces competitive-programming combinatorics Jun 8, 2026
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CF 1930D2 - Sum over all Substrings (Hard Version)

For every binary pattern $p$, we define $f(p)$ as the minimum number of 1s in another binary string $q$ of the same length such that every position of $p$ can "justify" its value by looking at some interval of $q$ containing that position.
codeforces competitive-programming bitmasks divide-and-conquer dp dsu greedy implementation strings Jun 8, 2026
Practice › Codeforces Solutions › think-cell Round 1 ›

CF 1930E - 2..3...4.... Wonderful! Wonderful!

We start with the array $$[1,2,3,dots,n].$$ A value $k$ is fixed for the whole process. In one operation we choose a subsequence of length $2k+1$. Among those chosen elements, we delete the first $k$ and the last $k$, keeping only the middle one.
codeforces competitive-programming combinatorics dp math Jun 8, 2026
Practice › Codeforces Solutions › think-cell Round 1 ›

CF 1930A - Maximise The Score

We are given a list of 2n positive integers, and we need to perform exactly n moves. Each move consists of picking two numbers from the list, adding the smaller of the two to our score, and removing both numbers from the list.
codeforces competitive-programming greedy sortings Jun 8, 2026