CPMagical CP Library

Problem solution · C++

Enumerate Primes

Enumerate Primes: a C++ solution using direct simulation. Learn the idea, check the complexity, and read the full code, with credit to NyaanNyaan Competitive Programming Library.

Technique
Direct simulation
Source
NyaanNyaan Competitive Programming Library
Length
21 lines
Start with the idea.

Try the problem first. If you get stuck, read the approach below, then write your own solution. The full code is at the bottom.

Approach

Direct simulation

For Enumerate Primes, the implementation follows the problem’s operations directly while maintaining only the state needed for the next decision.

  1. Translate each rule into one explicit state update.
  2. Maintain the invariant after every processed item.
  3. Return the accumulated state once all relevant input has been handled.

Code notes

  • 21 lines of C++ from the credited upstream file yosupo-prime-table.test.cpp.
  • The implementation keeps its working state in language-native values and containers.
  • No explicit loop blocks detected.

Complexity

Count the number and nesting of passes over the input, then include the maintained containers in the memory estimate.

Check the problem constraints before deciding whether this complexity will pass.

Source

Code and credit

This code comes from NyaanNyaan Competitive Programming Library by NyaanNyaan and is used under the CC0-1.0 licence.

Open problem ↗Original source ↗
Full codeEnumerate Primes · C++C++
Use this to learn the idea, then write your own version.
#define PROBLEM "https://judge.yosupo.jp/problem/enumerate_primes" #include "../../template/template.hpp"#include "../../prime/prime-enumerate.hpp"#include "../../misc/fastio.hpp" using namespace Nyaan; void Nyaan::solve() {  int N, A, B;  rd(N, A, B);  auto sieve = prime_enumerate(N);  int x = (sz(sieve) + A - B - 1) / A;  wt(sz(sieve));  wt(' ');  wt(x);  wt('\n');  rep(i, x) {    if (i) wt(' ');    wt(sieve[i * A + B]);  }  wt('\n');}

Keep practising

Did this explanation save you time? I'm a Grade 11 student building this free library to make difficult algorithms easier to understand.

Buy me a coffee ↗