Codeforces Round 869 (Div. 1)

Solutions for Codeforces Round 869 (Div. 1) (contest 1817). 2/5 problems verified against sample I/O. Difficulty range: 1500-3400.

5 items

Codeforces Round 869 (Div. 1)

Type: Div. 1 | Problems: 5 | Verified: 2/5 | Rating range: 1500-3400 | Time: 9m 23s

Problem Name Rating Tags Solve Time Verified
A Almost Increasing Subsequence 1500 binary-search, data-structures, greedy 3m 24s ✗
B Fish Graph 1900 brute-force, constructive-algorithms, dfs-and-similar 1m 39s ✗
C Similar Polynomials 2400 combinatorics, math 1m 21s ✓
D Toy Machine 2700 constructive-algorithms, games, implementation 1m 9s ✓
E Half-sum 3400 brute-force, divide-and-conquer, greedy 1m 50s ✗
Practice › Codeforces Solutions › Codeforces Round 869 (Div. 1) ›

CF 1817E - Half-sum

We are given a multiset of non-negative integers. At each step, we can take any two numbers, remove them, and insert their average back into the multiset.
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Practice › Codeforces Solutions › Codeforces Round 869 (Div. 1) ›

CF 1817A - Almost Increasing Subsequence

The failure is not a subtle edge-case bug. It is a complete mismatch between the problem being solved and the algorithm being applied.
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Practice › Codeforces Solutions › Codeforces Round 869 (Div. 1) ›

CF 1817D - Toy Machine

We are given a two-row toy machine with an odd number $n$ of cells in each row. The top row initially holds $n-2$ toys, placed in all cells except the two corners. The bottom row is mostly empty, with the exception that its leftmost, rightmost, and central cells are blocked.
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Practice › Codeforces Solutions › Codeforces Round 869 (Div. 1) ›

CF 1817B - Fish Graph

We are given an undirected simple graph, and we are allowed to choose any subset of its edges to form a new graph. The task is to determine whether we can extract a very specific structure called a fish graph.
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Practice › Codeforces Solutions › Codeforces Round 869 (Div. 1) ›

CF 1817C - Similar Polynomials

We are given two polynomials, $A(x)$ and $B(x)$, of the same degree $d$. Instead of the coefficients, we are provided their evaluations at the first $d+1$ integers, i.e., $A(0), A(1), dots, A(d)$ and $B(0), B(1), dots, B(d)$, all modulo $10^9+7$.
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