Codeforces Round 857 (Div. 1)

Solutions for Codeforces Round 857 (Div. 1) (contest 1801). 2/7 problems verified against sample I/O. Difficulty range: 1600-3400.

7 items

Codeforces Round 857 (Div. 1)

Type: Div. 1 | Problems: 7 | Verified: 2/7 | Rating range: 1600-3400 | Time: 16m 53s

Problem Name Rating Tags Solve Time Verified
A The Very Beautiful Blanket 1600 bitmasks, constructive-algorithms 2m 17s ✗
B Buying gifts 1800 data-structures, greedy, sortings 1m 44s ✗
C Music Festival 1900 binary-search, data-structures, dp 4m 24s ✗
D The way home 2100 binary-search, data-structures, dp 3m 31s ✗
E Gasoline prices 3000 data-structures, divide-and-conquer, dsu 1m 17s ✓
F Another n-dimensional chocolate bar 2700 dp, math, meet-in-the-middle 2m 8s ✗
G A task for substrings 3400 data-structures, string-suffix-structures, strings 1m 32s ✓
Practice › Codeforces Solutions › Codeforces Round 857 (Div. 1) ›

CF 1801G - A task for substrings

We are given a very long text string t and a set of distinct dictionary words s₁, s₂, ..., sₙ. For each query [l, r], we look only at the substring t[l..r]. Inside that interval we must count how many substrings are equal to one of the dictionary words.
codeforces competitive-programming data-structures string-suffix-structures strings Jun 9, 2026
Practice › Codeforces Solutions › Codeforces Round 857 (Div. 1) ›

CF 1801F - Another n-dimensional chocolate bar

We are given a chocolate bar in n dimensions. Along each dimension, the bar is already divided into discrete units: for dimension i, there are ai units. Vasya wants to cut the chocolate further along these pre-existing divisions to produce at least k pieces.
codeforces competitive-programming dp math meet-in-the-middle number-theory Jun 9, 2026
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CF 1801D - The way home

We are given a directed network of cities where each city has a per-day income, and each flight has a fixed cost. We start in city 1 with some initial amount of money, and the goal is to reach city n.
codeforces competitive-programming binary-search data-structures dp graphs greedy shortest-paths sortings Jun 9, 2026
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CF 1801C - Music Festival

The reason your solution produces no output is that it never actually writes to stdout. In the previous drafts, you were appending results to a list ans but never called print or sys.stdout.write. This is why the program runs without error but shows an empty output.
codeforces competitive-programming binary-search data-structures dp greedy sortings Jun 9, 2026
Practice › Codeforces Solutions › Codeforces Round 857 (Div. 1) ›

CF 1801E - Gasoline prices

We are given a country, Berland, structured as a tree of cities rooted at city 1. Each city has a gas station with a price range $[li, ri]$. Every year, the king’s two sons inspect gasoline prices along two paths of equal length.
codeforces competitive-programming data-structures divide-and-conquer dsu hashing trees Jun 9, 2026
Practice › Codeforces Solutions › Codeforces Round 857 (Div. 1) ›

CF 1801A - The Very Beautiful Blanket

We are asked to construct an $n times m$ grid filled with integers such that a specific XOR condition holds for every $4 times 4$ subgrid.
codeforces competitive-programming bitmasks constructive-algorithms Jun 9, 2026
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CF 1801B - Buying gifts

We are given several independent test cases. In each test case, there are $n$ departments, and each department offers two possible prices $ai$ and $bi$.
codeforces competitive-programming data-structures greedy sortings Jun 9, 2026