Bubble Cup 12 - Finals [Online Mirror, unrated, Div. 1]

9 problems from Bubble Cup 12 - Finals [Online Mirror, unrated, Div. 1] (contest 1218), difficulty 1500-3000. 4/9 solutions verified against sample I/O.

9 items

Bubble Cup 12 - Finals [Online Mirror, unrated, Div. 1]

Div. 1 | 9 problems | 4/9 verified | Difficulty 1500-3000 | 34m 41s

# Problem Rating Tags Accepted Time ✓
A BubbleReactor 2800 dp, graphs 180 3m 35s
B Guarding warehouses 3000 data-structures, geometry 95 3m 5s
C Jumping Transformers 2600 dp 217 3m 5s
D Xor Spanning Tree 2400 divide-and-conquer, fft, graphs 600 5m 2s
E Product Tuples 2500 divide-and-conquer, fft 475 3m 29s ✓
F Workout plan 1500 data-structures, greedy 3,191 5m 15s ✓
G Alpha planetary system 3000 constructive-algorithms, graphs, shortest-paths 163 4m 33s
H Function Composition 2900 dfs-and-similar 157 4m 2s ✓
I The Light Square 2100 2-sat, dfs-and-similar, greedy 743 2m 35s ✓
Practice › Codeforces Solutions › Bubble Cup 12 - Finals [Online Mirror, unrated, Div. 1] ›

CF 1218I - The Light Square

We are given three ingredients that define a transformation problem on a binary grid. First is an initial $N times N$ board of lights, each cell either on or off. Second is a target $N times N$ configuration we want to reach.
codeforces competitive-programming 2-sat dfs-and-similar greedy Jun 15, 2026
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CF 1218G - Alpha planetary system

We are given a network of spaceports connected by undirected shuttle routes. Each spaceport belongs to exactly one of three planets labeled X, Y, or Z. Every shuttle connects two different spaceports, and only connections between different planets exist.
codeforces competitive-programming constructive-algorithms graphs shortest-paths Jun 15, 2026
Practice › Codeforces Solutions › Bubble Cup 12 - Finals [Online Mirror, unrated, Div. 1] ›

CF 1218D - Xor Spanning Tree

We are given an undirected graph where each edge represents a wormhole between two planets and has a repair cost.
codeforces competitive-programming divide-and-conquer fft graphs Jun 15, 2026
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CF 1218E - Product Tuples

We are given an array of values, and each query asks us to evaluate a very specific symmetric polynomial built from a transformed version of that array. For a fixed number $q$, we first convert every element $ai$ into $bi = q - ai$.
codeforces competitive-programming divide-and-conquer fft Jun 15, 2026
Practice › Codeforces Solutions › Bubble Cup 12 - Finals [Online Mirror, unrated, Div. 1] ›

CF 1218A - BubbleReactor

We are given an undirected graph with $N$ vertices and exactly $N$ edges, and no pair of vertices is connected by more than one edge.
codeforces competitive-programming dp graphs Jun 15, 2026
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CF 1218B - Guarding warehouses

We are given a set of non-overlapping convex polygonal regions in the plane. Each polygon represents a warehouse. Bob stands at the origin, and for every point inside any warehouse we want to know whether Bob can “see” it using a special optical device.
codeforces competitive-programming data-structures geometry Jun 15, 2026
Practice › Codeforces Solutions › Bubble Cup 12 - Finals [Online Mirror, unrated, Div. 1] ›

CF 1218C - Jumping Transformers

We are moving through a grid from the top-left cell to the bottom-right cell, and each second we can only move either one step to the right or one step down. Any valid path is therefore a monotone path with exactly $N + M - 2$ moves.
codeforces competitive-programming dp Jun 15, 2026
Practice › Codeforces Solutions › Bubble Cup 12 - Finals [Online Mirror, unrated, Div. 1] ›

CF 1218F - Workout plan

Alan follows a fixed schedule of gym visits over $N$ days. On day $i$, he must lift exactly $X[i]$ grams, and he starts with a base strength $K$. He can permanently increase his strength by buying a pre-workout drink on any day he visits a gym.
codeforces competitive-programming data-structures greedy Jun 13, 2026
Practice › Codeforces Solutions › Bubble Cup 12 - Finals [Online Mirror, unrated, Div. 1] ›

CF 1218H - Function Composition

We are given a directed functional graph defined by an array A. From every node i, there is exactly one outgoing edge to A[i]. Repeated application of this mapping defines a process where starting from a node x, we move along the graph m times.
codeforces competitive-programming dfs-and-similar Jun 13, 2026