Codeforces Round 684 (Div. 1)

Solutions for Codeforces Round 684 (Div. 1) (contest 1439). 2/6 problems verified against sample I/O. Difficulty range: 1500-3500.

6 items

Codeforces Round 684 (Div. 1)

Type: Div. 1 | Problems: 6 | Verified: 2/6 | Rating range: 1500-3500 | Time: 25m 53s

Problem	Name	Rating	Tags	Solve Time	Verified
A1	Binary Table (Easy Version)	1500	constructive-algorithms, implementation	2m 8s	✗
A2	Binary Table (Hard Version)	1900	constructive-algorithms, graphs, greedy	12m 49s	✗
B	Graph Subset Problem	2600	constructive-algorithms, data-structures, graphs	6m 10s	✗
C	Greedy Shopping	2600	binary-search, data-structures, divide-and-conquer	1m 49s	✓
D	INOI Final Contests	3100	combinatorics, dp, fft	1m 8s	✓
E	Cheat and Win	3500	bitmasks, data-structures, games	1m 49s	✗

Practice › Codeforces Solutions › Codeforces Round 684 (Div. 1) ›

CF 1439A2 - Binary Table (Hard Version)

We are given a grid of zeros and ones with dimensions n by m. Each cell can either be off (0) or on (1). Our goal is to turn all the ones into zeros using a specific operation.

Practice › Codeforces Solutions › Codeforces Round 684 (Div. 1) ›

CF 1439E - Cheat and Win

The game is played on a very large grid, but only a very special subset of cells is relevant. A cell $(x, y)$ is considered valid only when the bitwise condition $x & y = 0$ holds.

Practice › Codeforces Solutions › Codeforces Round 684 (Div. 1) ›

CF 1439B - Graph Subset Problem

Ah, now the issue is clear. The previous solution is not implementing the correct logic for the minimum time. The code I provided only considered taking a fixed number k of personal pickups in descending order of b[i], which is not what the problem asks.

Practice › Codeforces Solutions › Codeforces Round 684 (Div. 1) ›

CF 1439D - INOI Final Contests

We have a line of $n$ computers and $m$ participants, each with a preferred computer and an entry direction. Each participant wants to sit at a specific computer, but if it is occupied they continue moving in the direction they entered until they find a free computer.

Practice › Codeforces Solutions › Codeforces Round 684 (Div. 1) ›

CF 1439C - Greedy Shopping

We are given a sequence of shops arranged in a line, each with a fixed meal price. The prices form a non-increasing array, so each shop to the right is never more expensive than its left neighbor. There are two types of operations we need to support.

Practice › Codeforces Solutions › Codeforces Round 684 (Div. 1) ›

CF 1439A1 - Binary Table (Easy Version)

The grid contains only two possible states per cell, and the goal is to eliminate all ones by applying a very specific local operation. Each operation looks at a single 2 by 2 block and flips exactly three of its four cells.