Codeforces Round 688 (Div. 2)

Solutions for Codeforces Round 688 (Div. 2) (contest 1453). 3/6 problems verified against sample I/O. Difficulty range: 800-2700.

6 items

Codeforces Round 688 (Div. 2)

Type: Div. 2 | Problems: 6 | Verified: 3/6 | Rating range: 800-2700 | Time: 24m 16s

Problem	Name	Rating	Tags	Solve Time	Verified
A	Cancel the Trains	800	implementation	1m 25s	✓
B	Suffix Operations	1400	constructive-algorithms, implementation	11m 6s	✓
C	Triangles	1700	greedy, implementation	6m 32s	✓
D	Checkpoints	1900	brute-force, constructive-algorithms, greedy	1m 49s	✗
E	Dog Snacks	2300	binary-search, dfs-and-similar, dp	1m 48s	✗
F	Even Harder	2700	dp	1m 36s	✗

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CF 1453B - Suffix Operations

We are given an array of integers and a machine that can increment or decrement all elements of a suffix of the array by 1. A suffix is any contiguous segment that includes the last element. Our goal is to make all elements equal using as few operations as possible.

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CF 1453F - Even Harder

We can view the game as a directed graph laid out on a line of positions from 1 to n. From position i, the player may jump forward to any position j such that j is strictly greater than i and at most i + a[i].

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CF 1453C - Triangles

We are given a square board of size n × n where each cell contains a digit between 0 and 9. For each digit d, we want to find a triangle whose vertices are the centers of cells containing d, with at least one side parallel to the board edges, such that the area of this…

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CF 1453E - Dog Snacks

We are given a tree with $n$ vertices, each vertex containing a snack. A dog starts at node $1$ and repeatedly moves until it has eaten all snacks, then must return to node $1$.

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CF 1453D - Checkpoints

The problem asks us to design a sequence of game stages and checkpoints so that a player with a 50% chance of beating any stage has an exact expected number of tries over the whole game. Every stage may or may not have a checkpoint, and the first stage always has one.

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CF 1453A - Cancel the Trains

We are asked to manage a train system on a 100×100 grid. Trains can move either vertically from the bottom to the top or horizontally from the left to the right.