Codeforces Round 976 (Div. 2) and Divide By Zero 9.0

Solutions for Codeforces Round 976 (Div. 2) and Divide By Zero 9.0 (contest 2020). 3/6 problems verified against sample I/O. Difficulty range: 800-2900.

6 items

Codeforces Round 976 (Div. 2) and Divide By Zero 9.0

Type: Div. 2 | Problems: 6 | Verified: 3/6 | Rating range: 800-2900 | Time: 9m 28s

Problem	Name	Rating	Tags	Solve Time	Verified
A	Find Minimum Operations	800	bitmasks, brute-force, greedy	1m 24s	✓
B	Brightness Begins	1200	binary-search, math	1m 34s	✓
C	Bitwise Balancing	1400	bitmasks, hashing, implementation	2m 10s	✗
D	Connect the Dots	1800	brute-force, dp, dsu	1m 16s	✓
E	Expected Power	2000	bitmasks, dp, math	2m 32s	✗
F	Count Leaves	2900	dp, math, number-theory	32s	✗

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CF 2020E - Expected Power

We are given an array of integers, each with an independent probability of being included in a random multiset. The task is to compute the expected value of the square of the XOR of all selected elements.

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CF 2020F - Count Leaves

Codeforces 2020F: Count Leaves

Practice › Codeforces Solutions › Codeforces Round 976 (Div. 2) and Divide By Zero 9.0 ›

CF 2020D - Connect the Dots

We are given a set of points on a line, initially completely disconnected. Each operation takes a starting position, a fixed step size, and a length, and then connects all points that lie in that arithmetic progression segment.

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CF 2020C - Bitwise Balancing

We are given three non-negative integers b, c, and d. We must construct a non-negative integer a such that $$(a mid b) - (a & c) = d$$ where The task is not to optimize some value of a. Any valid a is acceptable. If no such value exists, we print -1.

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CF 2020B - Brightness Begins

We are given a process on a line of bulbs indexed from $1$ to $n$. Initially every bulb is on. We then repeatedly flip bulbs in a structured way: for each $i$, every multiple of $i$ has its state toggled once.

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CF 2020A - Find Minimum Operations

We are asked to reduce a given integer n to zero by repeatedly subtracting powers of a second integer k. Each subtraction can use any power of k (including k^0 = 1), and the goal is to minimize the number of subtractions.