////////////////////////////////////////////////////////////// // Code using a stack, to check if 3 types of braces "()", // "[]", "{}". are valid in an expression. // // Solution of mine at codewars.com. // Author: Karl T. // Date: 06/07/2017 (updated 17/02/18) ///////////////////////////////////////////////////////////// #include #include #include bool ValidBraces(std::string braces) { std::stack brace; brace.push(' '); // push a dummy character in case the expression starts with a closing brace for(int i = 0; i < braces.length(); ++i) { if(braces[i] == '(') brace.push('('); else if(braces[i] == '{') brace.push('{'); else if(braces[i] == '[') brace.push('['); else if(braces[i] == ')') { if(brace.top() == '(') brace.pop(); else return false; } else if(braces[i] == '}') { if(brace.top() == '{') brace.pop(); else return false; } else if(braces[i] == ']') { if(brace.top() == '[') brace.pop(); else return false; } } } int main() { std::string b1 = "(a){}[b]"; // valid std::string b2 = "(}aa"; //invalid std::string b3 = "[(hello])"; // invalid std::string b4 = "([aa{hello}])"; // valid std::cout << b1 << " is " << (ValidBraces(b1) ? ("valid.") : ("invalid.")) << std::endl; std::cout << b2 << " is " << (ValidBraces(b2) ? ("valid.") : ("invalid.")) << std::endl; std::cout << b3 << " is " << (ValidBraces(b3) ? ("valid.") : ("invalid.")) << std::endl; std::cout << b4 << " is " << (ValidBraces(b4) ? ("valid.") : ("invalid.")) << std::endl; return 0; }

[Validity of 3 Types of Braces Using a Stack]