/* Various ways to find the length of the string without using string length functions (strlen for C and string.size() in C++). I have also avoided reading the string into C++ container and then obtain the string size using container size() methods. The last two methods requires user input, so on input prompt enter two strings in separate lines before pressing submit. All methods with predefined strings can be easily converted to take user input. And I am sure I have missed few more ways :) */ #include #include #include #include #include constexpr size_t Strlen(char const* a){ return !*a?0:1+Strlen(a+1);} int main() { // 1. std::string str{"sololearn"}; std::cout << "1. string = " << str << " len = " << str.end() - str.begin() << "\n"; // 2. compile time constexpr char const* pstr = "sololearn"; std::cout << "2. string = " << pstr << " len = " << Strlen(pstr) << "\n"; static_assert(9 == Strlen(pstr)); // 3. runtime std::cout << "3. string = " << str << " len = " << Strlen(str.c_str()) << "\n"; // 4. size_t len{0}; char const* sptr(str.c_str()); while(*sptr++) len++; std::cout << "4. string = " << str << " len = " << len << "\n"; // 5. len = 0; sptr = str.c_str(); std::cout << "5. string = "; for(size_t i=0; *sptr; std::cout << *sptr++ , ++len); std::cout <<" len = " << len << "\n"; // 6. len = 0; std::cout << "6. string = "; for(auto it(str.begin()); it!=str.end(); std::cout << *it++ , ++len); std::cout <<" len = " << len << "\n"; // 7. std::stringstream ss(str); ss.seekg(0, ss.end); std::cout << "7. string = " << str << " len = " << ss.tellg() << "\n"; // 8. char const cstr[]{"sololearn"}; std::cout << "8. string = " << str << " len = " << sizeof(cstr)-1 << "\n"; // 9. std::cout << "9. string = "; if(size_t len = printf("sololearn")){ std::cout << " len = " << len << "\n";} // 10. char buff[20]; std::cin.getline(buff, 20); std::cout << "10. string = " << buff << " len = " << std::cin.gcount()-1 << "\n"; // 11. STL // can use std::count_if len = 0; std::cout << "11. string = "; std::for_each(std::istream_iterator(std::cin), std::istream_iterator{},[&](char c ){ std::cout << c; len++;}); std::cout << " len = " << len << "\n"; return 0; } #define x std::cin>> // trigger cin

string_length_without_using_length_func.cpp