Freaks City

Preface This virtual contest didn't go as smoothly as expected. I spent longer than anticipated on problem B. For problem D, I identified the solution approach quickly but failed to account for several edge cases, resulting in three wrong submissions. Moving forward, I need to pay closer attention to edge cases during competition and work throu ...

A. Gardener and the Capybaras Given a string composed of characters 'a' and 'b', split it into three non-empty substrings. The goal is to make the middle substring lexicographically either the smallest or the largest among the three. Output any valid split or :( if impossible. Approach: The presence of only 'a' and 'b' is not restrictive. For t ...

This problem requires counting the number of zeros between the first and last occurrence of 1 in an array. #include <bits/stdc++.h> using namespace std; typedef long long ll; void solve() { int n; cin >> n; vector<int> arr(n); int firstOne = -1, lastOne = -1; for (int i = 0; i < n; i++) { ...

A - Long Comparison To compare two numbers represented as x1 * 10^p1 and x2 * 10^p2, first compare their total digit lengths: len(x1) + p1 vs len(x2) + p2. If unequal, the result is immediate. Otherwise, reduce both exponents by their minimum to ensure at least one becomes zero. Then scale the base integers accordingly and compare directly. Sin ...

Contest Overview This round was relatively straightforward, so this editorial will focus on both the technical problem solutions and the interesting sequence of events during the contest. Problem A - Subset Mex Problem Statement: Given a set a with |a| = n, partition it into two sets A and B to maximize mex(A) + mex(B). Multiple test cases. Con ...

CF472D: Reconstructing a Tree from Pairwise Distances A key observation is that the vertex closest to node 1 must be its direct child. This serves as the foundation for a recursive reconstruction strategy. Define a function check_subtree(v, parent) that attempts to build the subtree rooted at v. The logic relies on identifying the children of v ...

Given two arithmetic progressions $A_i = a_1 i + b_1$ and $B_i = a_2 i + b_2$ for $i \in \mathbb{N}$, and integers $l \leq r$, determine how many integers $n \in [l, r]$ appear in both sequences. We seek integer solutions $(x, y) \in \mathbb{N}^2$ to the equation: $$ a_1 x + b_1 = a_2 y + b_2 $$ Rewriting gives the linear Diophantine equation: ...

A. Be Positive Count how many elements are negative. If the amount is odd, flip one more element so the product becomes positive. void solve() { int n; cin >> n; int neg = 0; for (int i = 0; i < n; ++i) { int v; cin >> v; if (v < 0) ++neg; } cout << (neg & 1 ? neg + 1 : neg) <&l ...

Problem A: Operations with Inversions Greedy solution. Skipped for brevity. Problem B: Optimal Shifts Greedy solution. Skipped for brevity. Problem C: Odd Process Problem Statement: You have n numbers, each with a value a_i. You need to perform k rounds of operations where you can place a number into a bag (each number can only be placed once). ...

Problem Overview Given n employees and m available languages, each employee may know zero or more languages. Teaching a single language to a single employee costs 1 unit. The task is to determine the minimum total cost required so that every employee can communicate with every other employee (either directly or indirectly). Understanding Commun ...