/* Here's an interesting challenge for those interested: find my number! I will leave the clues here, and your job is to write a program to figure out the number! Seems simple enough right?Cool! Let's have some fun! Between 1 and 1000, there is only 1 number that meets the following criteria: 1. The number has two or more digits. 2. The number is prime. 3. The number does NOT contain a 1 or 7 in it. 4. The sum of all of the digits is less than or equal to 10. 5. The first two digits add up to be odd. *6. The second to last digit is even and greater than 1. 7. The last digit is equal to how many digits are in the number. So what's my number? Programs are better than proofs here! {^_^} *Clarification: (So if the number is 2 or 3 digits, you want the digit in the 10s spot) This implementation show how to make a simple task complex, but when you are trying out something new, then it's worth the effort :) https://www.sololearn.com/post/128588/?ref=app */ #include #include #include #include #include #include #include using namespace std; // overloads | operator and apply pipe_fun // to the container (Lhs) and returns a new // container template struct pipe_func { F f; template friend auto operator|(Lhs&& lhs, pipe_func rhs ) { return rhs.f(forward(lhs)); } }; // helper function that returns pipe_func template pipe_func(Func)->pipe_func; //Filter returns a pipe function containing // a lambda function that will apply // std::copy_if to the source container and // returns a new target container of same // type containing the filtered elements by // applying the predicate P auto Filter = [](auto P) { return pipe_func{[=](auto source) { decltype(source) res; copy_if(begin(source), end(source),back_inserter(res), P); return res; }}; }; auto ApplyEach = [](auto P){ return pipe_func{[=](auto&& source) { for_each(begin(source),end(source), P); return source; }}; }; // returns true if a number is prime false // otherwise // checks only odd numbers other than 2 auto isPrime = [](auto num){ if (num < 2) return false; if (num == 2) return true; if (!(num & 1)) return false; for(int i{3};i<=sqrt(num)+1;i+=2){ if(!(num % i)) return false; } return true; }; // Returns true if the number does not contain 1 or 7 auto No_digit_one_or_seven = [](auto num) { auto [p100,p10,p1] = make_tuple(num/100, num%100/10, num%10); return (p100 != 1 && p100 != 7) && (p10 != 1 && p10 != 7) && (p1 != 1 && p1 != 7); }; // check if number length is greater than 2 auto isNumlengthGT2 = [](auto num){ return num > 9; }; // return true if sum of digits of a number // is less than or equal 10, false otherwise auto Digits_sum_lte_10 = [](auto num) { return(num/100+num%100/10+num%10)<=10; }; // returns true if the sum of first two // digits of a number is odd, false // otherwise auto First_2Digits_sum_odd = [](auto num) { return (num/100 + num%100/10) & 1; }; // returns true if the second digit from // last is even and greater than 1, false // otherwise auto Sdflast_is_even_and_gt1 = [](auto num) { num = num/10 % 10; return !(num & 1) && num > 1; }; // returns true if the last digit of a // number equals number of digits in the // number, false otherwise auto Last_digit_eq_num_len = [](auto num){ return (floor(log10(num))+1) == num%10; }; // simply outputs the value auto Cout = [](auto val) { cout << setw(4) << left << val << "\n"; }; int main() { vector nums(1000); // fill with increasing numbers iota(begin(nums), end(nums), 1); // applying predicates successively on // vector nums | Filter(isNumlengthGT2) | Filter(isPrime) | Filter(No_digit_one_or_seven) | Filter(Digits_sum_lte_10) | Filter(First_2Digits_sum_odd) | Filter(Sdflast_is_even_and_gt1) | Filter(Last_digit_eq_num_len) | ApplyEach(Cout); return 0; }

[Challenge] Ace_Number.cpp