Freaks City

Number Theory Primality Testing via Trial Division #include <iostream> using namespace std; bool isPrime(int num) { if (num < 2) return false; for (int d = 2; d <= num / d; ++d) if (num % d == 0) return false; return true; } int main() { int queries; cin >> queries; while (queries--) { ...

Resource Redistribution with Asymmetric Operations Given a sequence (a) of length (n) and two positive integers (x, y) where (y \le x). You may repeatedly pick two elements and transfer resources: subtract (x) from one and add (y) to the other, provided the first remains non‑negative. Determine the maximum possible value of any element after op ...

Task 1 – Factor Splitting Given a positive integer n that is the product of two distinct primes, output the larger one. Input: One integer n (≤ 2·109). Output: The larger prime factor. Observation: The first divisor (other than 1) must be the smaller prime, so the answer is n / i once the smallest i > 1 with n % i == 0 is found. #include &lt ...

Problem B: Arbitrary Base Conversion This code converts a number from one arbitrary base to another. Implementation #include <stdio.h> #include <string.h> // Convert from base `src_base` string `src_num` to decimal integer. int convert_to_decimal(int src_base, const char *src_num) { int result = 0; int place_value = 1; ...

Mathematical Algorithms Fast Exponentiation Reduces the time complexity of computing powers to logarithmic time by leveraging binary decomposition of the exponent. long long binary_pow(long long base, long long exp, long long mod) { long long res = 1; base %= mod; while (exp > 0) { if (exp & 1) res = (res * base) % mo ...

Number Theory 1.1 Chinese Remainder Theorem Problem Statement Given a system of congruences: \[ \begin{cases} x \equiv a_1 \pmod{b_1} \\ x \equiv a_2 \pmod{b_2} \\ \vdots \\ x \equiv a_n \pmod{b_n} \end{cases} \] Find the smallest positive integer solution for \(x\), where \(b_i\) (for \(i \in [1,n]\)) are pairwise coprime. Theoretical Analy ...

A Given a sequence ${a_n}$, select the largest possible subset such that no two selected elements sum to a prime number. Constraints: $T \leq 4$, $n \leq 750$, $a_i \leq 10^9$. Identical values can be merged into counts. Note that at most one instance of 1 may be included. This becomes a bipartite graph problem: odd numbers connect to the sourc ...

Lucas Theorem Mathematical Statement Given prime $p$, the following congruence holds: $$\binom{n}{m} \equiv \binom{\lfloor n/p \rfloor}{\lfloor m/p \rfloor} \cdot \binom{n \bmod p}{m \bmod p} \pmod{p}$$ Proof Foundation Lemma 1 For prime $p$: $$\binom{p}{k} \equiv 0 \pmod{p} \text{ when } 0 < k < p$$ The numerator contains factor $p$, mak ...

Problem A: Digit Frequency Analysis Given a functon (f(x)) that counts the frequency of the most common digit in number (x), compute (\sum_{i=l}^{r}f(i)) for large ranges (up to (10^{18})). Approach: Represent digit counts as a state vector (S = {c_0, \dots, c_9}) Transform into frequency-of-counts representation (S' = {a_0, \dots, a_{18}}) Us ...

Probabilistic Path Enumeration in Directed Acyclic Graphs Given a directed acyclic graph (DAG) consisting of $V$ vertices and $E$ edges, each edge $e_k$ possesses an independent activation probability $p_k$. The objective is to compute the expected number of functional paths originating from vertex $0$ and terminating at vertex $V-1$. A path is ...