Codeforces Round 969 (Div. 2)

Solutions for Codeforces Round 969 (Div. 2) (contest 2007). 3/6 problems verified against sample I/O. Difficulty range: 800-2300.

6 items

Codeforces Round 969 (Div. 2)

Type: Div. 2 | Problems: 6 | Verified: 3/6 | Rating range: 800-2300 | Time: 17m 28s

Problem	Name	Rating	Tags	Solve Time	Verified
A	Dora's Set	800	greedy, math, number-theory	2m 16s	✓
B	Index and Maximum Value	900	data-structures, greedy	1m 31s	✓
C	Dora and C++	1500	math, number-theory	5m 16s	✗
D	Iris and Game on the Tree	1700	games, graphs, greedy	5m 47s	✗
E	Iris and the Tree	1800	brute-force, data-structures, dfs-and-similar	1m 33s	✗
F	Eri and Expanded Sets	2300	binary-search, data-structures, number-theory	1m 5s	✓

Practice › Codeforces Solutions › Codeforces Round 969 (Div. 2) ›

CF 2007D - Iris and Game on the Tree

We are given a tree rooted at vertex 1 where each node contains either a 0, 1, or an undecided value represented as ?.

Practice › Codeforces Solutions › Codeforces Round 969 (Div. 2) ›

CF 2007C - Dora and C++

We are given an array of integers and two fixed step sizes, $a$ and $b$. We can repeatedly pick any position and add either $a$ or $b$ to that element any number of times.

Practice › Codeforces Solutions › Codeforces Round 969 (Div. 2) ›

CF 2007F - Eri and Expanded Sets

For every subarray, we throw all of its values into a set, removing duplicates. Starting from that set, we may repeatedly pick two distinct elements whose average is an integer and add that average if it is not already present.

Practice › Codeforces Solutions › Codeforces Round 969 (Div. 2) ›

CF 2007E - Iris and the Tree

We are given a rooted tree with vertex 1 as the root. Each non-root vertex $i$ has a parent $pi$ and an unknown non-negative weight $ti$ on its connecting edge. The sum of all weights is $w$.

Practice › Codeforces Solutions › Codeforces Round 969 (Div. 2) ›

CF 2007A - Dora's Set

We start with all integers in the interval $[l,r]$. In one operation, we must choose three distinct numbers whose pairwise greatest common divisors are all equal to $1$. After choosing them, those three numbers are removed permanently.

Practice › Codeforces Solutions › Codeforces Round 969 (Div. 2) ›

CF 2007B - Index and Maximum Value

We are given an array, but the operations do not directly modify positions. Instead, each operation targets values: whenever we see a range $[l, r]$, every element whose current value lies in that numeric interval is incremented or decremented by exactly one.