Codeforces Round 175 (Div. 2)

5 problems from Codeforces Round 175 (Div. 2) (contest 285), difficulty 1100-2600. 2/5 solutions verified against sample I/O.

5 items

Codeforces Round 175 (Div. 2)

Div. 2 | 5 problems | 2/5 verified | Difficulty 1100-2600 | 9m 39s

#	Problem	Rating	Tags	Accepted	Time	✓
A	Slightly Decreasing Permutations	1100	greedy, implementation	14,137	2m 7s
B	Find Marble	1200	implementation	15,696	1m 43s	✓
C	Building Permutation	1200	greedy, implementation, sortings	26,325	1m 54s
D	Permutation Sum	1900	bitmasks, combinatorics, dp	1,675	2m 10s
E	Positions in Permutations	2600	combinatorics, dp, math	1,294	1m 45s	✓

Practice › Codeforces Solutions › Codeforces Round 175 (Div. 2) ›

CF 285C - Building Permutation

We are given an array of integers and we are allowed to modify it using unit increments or decrements. Each such operation costs one move. The goal is to transform the array into a permutation of size n, meaning we must end up with exactly the numbers from 1 to n, each used once.

Practice › Codeforces Solutions › Codeforces Round 175 (Div. 2) ›

CF 285B - Find Marble

We have a row of n glasses, each uniquely indexed from 1 to n. A marble starts under the glass at position s. Petya defines a permutation of the positions that determines how glasses are moved simultaneously during a shuffle.

Practice › Codeforces Solutions › Codeforces Round 175 (Div. 2) ›

CF 285E - Positions in Permutations

We are asked to count permutations of length n that have exactly k positions where the absolute difference between the value and its index is exactly 1. A permutation of length n is a sequence containing all integers from 1 to n in some order without repetition.

Practice › Codeforces Solutions › Codeforces Round 175 (Div. 2) ›

CF 285D - Permutation Sum

We are asked to count pairs of permutations (a, b) of length n such that their modular sum produces another valid permutation c. For each index i, c[i] = ((a[i]-1 + b[i]-1) mod n) + 1. This is a bijective operation, meaning every element of c must be unique and within 1 to n.

Practice › Codeforces Solutions › Codeforces Round 175 (Div. 2) ›

CF 285A - Slightly Decreasing Permutations

We are asked to construct a permutation of numbers from 1 to n that has exactly k positions where a number is greater than the number immediately after it. In other words, we need a sequence of length n where precisely k "descents" occur.