CodeTON Round 1 (Div. 1 + Div. 2, Rated, Prizes!)

9 problems from CodeTON Round 1 (Div. 1 + Div. 2, Rated, Prizes!) (contest 1656), difficulty 800-3500. 3/9 solutions verified against sample I/O.

9 items

CodeTON Round 1 (Div. 1 + Div. 2, Rated, Prizes!)

Div. 1+2 | 9 problems | 3/9 verified | Difficulty 800-3500 | 38m 59s

# Problem Rating Tags Accepted Time ✓
A Good Pairs 800 math, sortings 20,452 2m 23s ✓
B Subtract Operation 1100 data-structures, greedy, math 26,793 1m 49s ✓
C Make Equal With Mod 1200 constructive-algorithms, math, number-theory 21,003 1m 58s ✓
D K-good 1900 constructive-algorithms, math, number-theory 7,558 4m 51s
E Equal Tree Sums 2200 constructive-algorithms, dfs-and-similar, math 3,860 3m 11s
F Parametric MST 2600 binary-search, constructive-algorithms, graphs 1,219 4m 51s
G Cycle Palindrome 3200 constructive-algorithms, graphs, math 462 5m 59s
H Equal LCM Subsets 3200 data-structures, math, number-theory 796 3m 21s
I Neighbour Ordering 3500 constructive-algorithms, graphs 154 10m 36s
Practice › Codeforces Solutions › CodeTON Round 1 (Div. 1 + Div. 2, Rated, Prizes!) ›

CF 1656I - Neighbour Ordering

We are given a connected undirected graph, and we are allowed to choose, independently for every vertex, an ordering of its adjacent vertices.
codeforces competitive-programming constructive-algorithms graphs Jun 15, 2026
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CF 1656G - Cycle Palindrome

We are given an array of integers and we are allowed to reorder its indices using a very restricted type of permutation: a single cycle that visits every position exactly once before returning to the start.
codeforces competitive-programming constructive-algorithms graphs math Jun 15, 2026
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CF 1656H - Equal LCM Subsets

We are given two finite collections of very large positive integers, think of them as two bags of numbers. From each bag we are allowed to pick any non-empty subcollection. For each chosen subcollection, we compute the least common multiple of all its elements.
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CF 1656D - K-good

We are given a number $n$, and we want to check whether there exists an integer $k ge 2$ such that we can split $n$ into exactly $k$ positive integers with a special property: when each of those $k$ numbers is divided by $k$, all remainders must be different.
codeforces competitive-programming constructive-algorithms math number-theory Jun 15, 2026
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CF 1656F - Parametric MST

We are given an array of integers, and we build a complete graph where every pair of vertices is connected. The weight of an edge between vertices $i$ and $j$ depends on a parameter $t$ and is defined as a linear function in $t$: it has a fixed quadratic-looking term $ai aj$…
codeforces competitive-programming binary-search constructive-algorithms graphs greedy math sortings Jun 15, 2026
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CF 1656E - Equal Tree Sums

We are given a tree, and we must assign a nonzero integer to every vertex. The constraint is not about the whole tree sum, but about what happens when a vertex is removed. If we delete any vertex $v$, the tree splits into several connected components.
codeforces competitive-programming constructive-algorithms dfs-and-similar math trees Jun 15, 2026
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CF 1656A - Good Pairs

We are asked to find a "good pair" of indices in an array of positive integers. A good pair consists of two indices $i$ and $j$ such that, if you consider any element $ak$ in the array, the sum of distances from $ai$ to $ak$ and from $ak$ to $aj$ equals the distance from $ai$…
codeforces competitive-programming math sortings Jun 10, 2026
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CF 1656C - Make Equal With Mod

We are given an array of non-negative integers. In one operation, we choose an integer $x ge 2$ and simultaneously replace every element $ai$ with $ai bmod x$. The operation may be applied any number of times, including zero.
codeforces competitive-programming constructive-algorithms math number-theory sortings Jun 10, 2026
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CF 1656B - Subtract Operation

We start with an array of integers. In one operation, we pick an element, remove it from the array, and subtract its value from every remaining element. After exactly $n-1$ operations, only one number remains.
codeforces competitive-programming data-structures greedy math two-pointers Jun 10, 2026