Codeforces Round 861 (Div. 2)

7 problems from Codeforces Round 861 (Div. 2) (contest 1808), difficulty 900-2800. 4/7 solutions verified against sample I/O.

7 items

Codeforces Round 861 (Div. 2)

Div. 2 | 7 problems | 4/7 verified | Difficulty 900-2800 | 18m 4s

#	Problem	Rating	Tags	Accepted	Time	✓
A	Lucky Numbers	900	brute-force, implementation	20,611	2m 1s	✓
B	Playing in a Casino	1200	math, sortings	29,642	1m 24s	✓
C	Unlucky Numbers	1900	brute-force, dp, greedy	4,330	2m 28s
D	Petya, Petya, Petr, and Palindromes	2100	binary-search, brute-force, data-structures	2,706	2m 17s	✓
E1	Minibuses on Venus (easy version)	2200	combinatorics, divide-and-conquer, dp	1,599	4m 36s
E2	Minibuses on Venus (medium version)	2500	combinatorics, divide-and-conquer, dp	847	2m 45s
E3	Minibuses on Venus (hard version)	2800	brute-force, combinatorics, dp	575	2m 33s	✓

Practice › Codeforces Solutions › Codeforces Round 861 (Div. 2) ›

CF 1808E2 - Minibuses on Venus (medium version)

We are counting sequences of length n, where each position holds a digit in base k. So each ticket is just an array of length n with values from 0 to k-1.

Practice › Codeforces Solutions › Codeforces Round 861 (Div. 2) ›

CF 1808E1 - Minibuses on Venus (easy version)

We are counting digit sequences of fixed length in base $k$. Each ticket is just an array of $n$ numbers, each between $0$ and $k-1$. A ticket is considered valid if we can pick one position $i$ such that the digit at $i$ is equal to the sum of all other digits, taken modulo $k$.

Practice › Codeforces Solutions › Codeforces Round 861 (Div. 2) ›

CF 1808C - Unlucky Numbers

We are given multiple independent queries. Each query describes a contiguous range of integers from $l$ to $r$, and each integer in that range represents a starship identifier.

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CF 1808A - Lucky Numbers

We are given multiple queries. Each query describes a range of integers from $l$ to $r$, and each integer represents a candidate “starship number”.

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CF 1808E3 - Minibuses on Venus (hard version)

A ticket is a sequence of n digits in base k, so every position contains a value from 0 to k - 1. Let the total digit sum modulo k be $$S = a1 + a2 + dots + an pmod k.$$ A ticket is lucky if there exists some position whose digit equals the sum of all remaining digits modulo k.

Practice › Codeforces Solutions › Codeforces Round 861 (Div. 2) ›

CF 1808D - Petya, Petya, Petr, and Palindromes

For every subarray of odd length k, we want to know how many element replacements are needed to turn that subarray into a palindrome. The answer is the sum of those values over all length-k subarrays.

Practice › Codeforces Solutions › Codeforces Round 861 (Div. 2) ›

CF 1808B - Playing in a Casino

Each player receives a card containing m integers. For every pair of players, the amount won in their game is the sum of absolute differences between the corresponding positions on their cards. If player i has card values c[i][1...m] and player j has card values c[j][1...