Codeforces Round 678 (Div. 2)

Solutions for Codeforces Round 678 (Div. 2) (contest 1436). 3/6 problems verified against sample I/O. Difficulty range: 800-2800.

6 items

Codeforces Round 678 (Div. 2)

Type: Div. 2 | Problems: 6 | Verified: 3/6 | Rating range: 800-2800 | Time: 13m 27s

Problem	Name	Rating	Tags	Solve Time	Verified
A	Reorder	800	math	3m 26s	✓
B	Prime Square	900	constructive-algorithms, math	2m 44s	✗
C	Binary Search	1500	binary-search, combinatorics	1m 35s	✓
D	Bandit in a City	1900	binary-search, dfs-and-similar, graphs	1m 33s	✓
E	Complicated Computations	2400	binary-search, data-structures, two-pointers	2m 33s	✗
F	Sum Over Subsets	2800	combinatorics, math, number-theory	1m 36s	✗

Practice › Codeforces Solutions › Codeforces Round 678 (Div. 2) ›

CF 1436E - Complicated Computations

The key issue is that this is a constructive problem. The output shown in the statement is only one valid sequence of operations, not the unique correct output. Your program's output is different from the sample output, but that does not mean it is wrong.

Practice › Codeforces Solutions › Codeforces Round 678 (Div. 2) ›

CF 1436F - Sum Over Subsets

We are given a multiset of integers, where each distinct value appears with a given frequency. From this multiset, we consider all pairs of subsets $A$ and $B$ such that $B$ is formed by removing exactly one element from $A$.

Practice › Codeforces Solutions › Codeforces Round 678 (Div. 2) ›

CF 1436A - Reorder

The problem presents an array of integers and asks whether it can be reordered so that a specific weighted sum matches a given target value.

Practice › Codeforces Solutions › Codeforces Round 678 (Div. 2) ›

CF 1436D - Bandit in a City

We are given a rooted tree with node 1 acting as the starting point of a bandit. Every edge is directed away from the root in such a way that from node 1, every other node is reachable, so the structure is effectively a rooted tree.

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CF 1436B - Prime Square

Practice › Codeforces Solutions › Codeforces Round 678 (Div. 2) ›

CF 1436C - Binary Search

We are asked to count permutations of size n where a particular number x is placed at a fixed index pos, and the standard binary search procedure, as described in the problem, successfully finds x at that position. A permutation here is any ordering of the numbers 1 through n.