/* Self-destructive Numbers I had this silly thought yesterday while I was sitting down by the lake. Maybe it appeals to someone ☺ Let a digit 'd' be said to "annihilate" a digit 'e' if their sum is 10 (or 0 modulo 10). Zero annihilates itself. A positive integer 'n' is "reactive" if it has zeros or adjacent annihilating digits. For example 1374 is reactive, since 3 annihilates 7, but 1347 is not reactive because 3 and 7 are not adjacent. Reactive numbers can be reduced by letting annihilators react [remove from the number]. An empty number is set to 0. A number is said to be "self-destructive" if it reduces to 0. Examples: 1374 -> 14 10198 -> 18 1552089 -> 0 [self-destructive] Write a function to test a number for being self-destructive. What are the first few self-destructive numbers? Enter a number or press submit for default number = 1552089 https://www.sololearn.com/post/168288/?ref=app */ #include using namespace std; namespace { string const flt[]{"0","19","28","37","46","55","64","73","82","91"}; string filter10(string n){ size_t prev{0},curr{0}; string fstr; bool once{false}; for(auto it{begin(flt)};it!=end(flt);++it){ while((curr=n.find(it->c_str(), curr,it->size()))!=string::npos) { once = true; fstr += n.substr(prev, curr - prev); prev = curr + it->size(); curr += it->size(); } fstr += n.substr(prev); n = fstr; if(once) it=begin(flt),once=false; fstr.clear(); curr = prev = 0; }// end for return n.empty()? "Self Destructable" : n; } // end filter10 } // end namespace int main() { string n {"1552089"}; cin >> n; cout << "number " << n << " is " << filter10(n) << '\n'; cout << "List of Self Destructable numbers between 0 to 10000: \n"; for(int i{0}; i<10000; ++i) if(filter10(to_string(i)) == "Self Destructable") cout << i << '\n'; }

[Challenge] Self_Destructive_Numbers.cpp