#include #include #include #include #include #include using RSet = std::unordered_multiset; using RSSet = std::unordered_set; enum class NUM_ERROR{WRONG_LENGTH, SAME_DIGITS, NOT_NUMBER}; auto Sort=[](auto& C, bool asc=true){ if(asc) std::sort(C.begin(), C.end()); else sort(C.begin(), C.end(), std::greater());}; void Validate(auto const& in){ if(in.size()<2) throw NUM_ERROR::WRONG_LENGTH; if(std::all_of(in.begin(),in.end(), [=](char c){ if(std::isdigit(c)) return c == in.at(0); else throw NUM_ERROR::NOT_NUMBER;})) throw NUM_ERROR::SAME_DIGITS; } void Adjust(std::string& str, int sz) { std::stringstream ss; ss << std::setw(sz) << std::setfill('0') << std::right << str; ss >> str;} auto main()->int {std::string nsmax; std::cin>>nsmax; try { Validate(nsmax); } catch(NUM_ERROR const ne){ if(ne==NUM_ERROR::WRONG_LENGTH){ std::cout << "input number should consist at least two digits"; return 0; } if(ne==NUM_ERROR::SAME_DIGITS) { std::cout << "input number should consist at least two different digits"; return 0;} if(ne==NUM_ERROR::NOT_NUMBER){ std::cout << "invalid input number"; return 0; }} Sort(nsmax,false);std::string nsmin(nsmax); Sort(nsmin); RSet rset; int iter{}; do { int nmax(std::stoi(nsmax)); int nmin(stoi(nsmin)); int diff = nmax - nmin; ++iter; std::cout <1) { RSSet svrset; for(auto it=rset.begin();it!=rset.end();++it) { if(rset.count(*it)>1)svrset.emplace(*it);} std::cout<<"converged to : "; for(auto e:svrset) {std::cout << e << " ";} std::cout <<"in " << iter << " iterations"; break;} else rset.insert(diff); std::string diffs(std::to_string(diff)); if(diffs.size()

Kaprekar's_constant.cpp