Codeforces Round 815 (Div. 2)

6 problems from Codeforces Round 815 (Div. 2) (contest 1720), difficulty 800-2700. 3/6 solutions verified against sample I/O.

6 items

Codeforces Round 815 (Div. 2)

Div. 2 | 6 problems | 3/6 verified | Difficulty 800-2700 | 15m 22s

#	Problem	Rating	Tags	Accepted	Time	✓
A	Burenka Plays with Fractions	900	math, number-theory	24,361	2m 8s	✓
B	Interesting Sum	800	brute-force, data-structures, greedy	22,413	2m 18s	✓
C	Corners	1200	greedy, implementation	18,229	3m 5s
D1	Xor-Subsequence (easy version)	1800	bitmasks, brute-force, dp	6,709	2m 1s
D2	Xor-Subsequence (hard version)	2400	bitmasks, data-structures, dp	2,198	2m 51s
E	Misha and Paintings	2700	constructive-algorithms, data-structures, greedy	950	2m 59s	✓

Practice › Codeforces Solutions › Codeforces Round 815 (Div. 2) ›

CF 1720E - Misha and Paintings

We are given an $n times n$ grid of integers. Each cell initially contains some value, and we are allowed to perform an operation that selects any square submatrix and overwrites every cell inside it with a single chosen integer.

Practice › Codeforces Solutions › Codeforces Round 815 (Div. 2) ›

CF 1720D2 - Xor-Subsequence (hard version)

We are given an array of integers, and we want to choose a subsequence of indices. The chosen indices must be strictly increasing in position, but the values we compare are not just the array values themselves.

Practice › Codeforces Solutions › Codeforces Round 815 (Div. 2) ›

CF 1720D1 - Xor-Subsequence (easy version)

We are given an array of integers where each value is small, but the index range can be large. From this array we want to pick a subsequence of positions, keeping the indices strictly increasing.

Practice › Codeforces Solutions › Codeforces Round 815 (Div. 2) ›

CF 1720C - Corners

We are given a binary grid where each cell is either empty or contains a single unit. The only allowed move is to pick a 2 by 2 block and choose three of its four cells forming an L shape.

Practice › Codeforces Solutions › Codeforces Round 815 (Div. 2) ›

CF 1720B - Interesting Sum

We are given an array of integers, and we are allowed to pick a single contiguous segment inside it, but not the whole array. Once we choose this segment, the array is conceptually split into two parts: the chosen segment and everything outside it.

Practice › Codeforces Solutions › Codeforces Round 815 (Div. 2) ›

CF 1720A - Burenka Plays with Fractions

Each test case gives two fractions, $frac{a}{b}$ and $frac{c}{d}$. In one move, you are allowed to pick exactly one of the four numbers $a, b, c, d$ and multiply it by any nonzero integer.