Codeforces Round 719 (Div. 3)

8 problems from Codeforces Round 719 (Div. 3) (contest 1520), difficulty 800-2200. 6/8 solutions verified against sample I/O.

8 items

Codeforces Round 719 (Div. 3)

Div. 3 | 8 problems | 6/8 verified | Difficulty 800-2200 | 29m 45s

#	Problem	Rating	Tags	Accepted	Time	✓
A	Do Not Be Distracted!	800	brute-force, implementation	58,445	2m 30s	✓
B	Ordinary Numbers	800	brute-force, math, number-theory	49,618	4m 49s	✓
C	Not Adjacent Matrix	1000	constructive-algorithms	34,536	2m 18s	✓
D	Same Differences	1200	data-structures, hashing, math	64,435	2m	✓
E	Arranging The Sheep	1400	greedy, math	28,594	2m 19s	✓
F1	Guess the K-th Zero (Easy version)	1600	binary-search, interactive	14,386	8m 38s
F2	Guess the K-th Zero (Hard version)	2200	binary-search, constructive-algorithms, data-structures	3,347	4m 57s
G	To Go Or Not To Go?	2200	brute-force, dfs-and-similar, graphs	4,215	2m 14s	✓

Practice › Codeforces Solutions › Codeforces Round 719 (Div. 3) ›

CF 1520F1 - Guess the K-th Zero (Easy version)

We are given a hidden binary array of length $n$. We cannot see the array directly. Instead, we can ask queries on any interval $[l, r]$, and the system returns the number of ones in that segment.

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CF 1520F2 - Guess the K-th Zero (Hard version)

We are dealing with a hidden binary array of length $n$, where each position is either zero or one. The array does not change on its own, but it is modified by our own actions: every time we correctly identify the position of the current $k$-th zero from the left, that…

Practice › Codeforces Solutions › Codeforces Round 719 (Div. 3) ›

CF 1520B - Ordinary Numbers

We are given multiple queries, and each query consists of a single positive integer $n$. For each $n$, we need to count how many numbers in the range from 1 to $n$ have all digits identical in their decimal representation. These “ordinary” numbers have a very rigid structure.

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CF 1520G - To Go Or Not To Go?

We are asked to find the minimum time for Dima to travel from the top-left corner of a rectangular city grid to the bottom-right corner. The city is represented as an n × m grid where each cell has a value: -1 for blocked, 0 for free, and x 0 for a portal with cost x.

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CF 1520E - Arranging The Sheep

We have a one-dimensional board represented by a string. Each '' is a sheep and each '.' is an empty cell. In one move, a sheep can move exactly one position left or right into an adjacent empty cell.

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CF 1520D - Same Differences

We are given an array and must count how many index pairs $(i, j)$ with $i < j$ satisfy a very specific relationship between their values and positions.

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CF 1520A - Do Not Be Distracted!

Each test case gives a sequence of days, where every day is labeled with the task Polycarp worked on that day. The rule is simple: once he stops working on a task and switches to another one, he is never allowed to return to the old task.

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CF 1520C - Not Adjacent Matrix

We are asked to fill an $n times n$ square grid with the numbers from $1$ to $n^2$ such that no two horizontally or vertically neighboring cells contain consecutive integers. In other words, the difference between numbers in adjacent cells cannot be exactly one.