Educational Codeforces Round 173 (Rated for Div. 2)

7 problems from Educational Codeforces Round 173 (Rated for Div. 2) (contest 2043), difficulty 800-3000. 3/7 solutions verified against sample I/O.

7 items

Educational Codeforces Round 173 (Rated for Div. 2)

Div. 2 | 7 problems | 3/7 verified | Difficulty 800-3000 | 15m 21s

#	Problem	Rating	Tags	Accepted	Time	✓
A	Coin Transformation	800	brute-force, math	26,986	3m 13s	✓
B	Digits	1100	math, number-theory	21,728	2m 8s
C	Sums on Segments	1600	binary-search, brute-force, data-structures	11,195	1m 57s
D	Problem about GCD	1800	brute-force, flows, math	7,677	1m 48s	✓
E	Matrix Transformation	2300	bitmasks, brute-force, data-structures	1,826	2m 10s
F	Nim	2700	bitmasks, brute-force, combinatorics	906	2m 2s
G	Problem with Queries	3000	brute-force, data-structures, implementation	325	2m 3s	✓

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CF 2043G - Problem with Queries

We are given an array of integers and need to handle two types of queries. The first type updates a single element in the array. The second type asks for the number of pairs of indices within a specified subarray that contain different values.

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CF 2043F - Nim

We are asked to consider multiple rounds of the game Nim played on contiguous subarrays of an array of integers. Each integer represents a pile of stones.

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CF 2043E - Matrix Transformation

The failure you show is not enough to diagnose the algorithm itself. Let's trace what happened: The input contains 5 test cases: The program produced only: instead of: This means the code successfully processed the first test case and then terminated before handling the…

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CF 2043D - Problem about GCD

We are asked to find two numbers $A$ and $B$ inside a closed range $[l, r]$ such that their greatest common divisor is exactly $G$, and the distance $ The inputs $l$, $r$, and $G$ can be as large as $10^{18}$, which rules out any solution that iterates through the entire range…

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CF 2043A - Coin Transformation

We start with a single coin whose value is given by an integer $n$. The only allowed move takes a coin whose value is strictly greater than 3, and replaces it with exactly two coins, each having value equal to the floor of one quarter of the original value.

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CF 2043B - Digits

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CF 2043C - Sums on Segments

We are given an array where almost every element is either 1 or -1, with at most one element allowed to be any integer. Our task is to find all distinct sums of contiguous subarrays. The sum of a subarray is simply the sum of its elements.