#include #include using namespace std; // function check if a string is empty bool isEmpty(string str) { if(str.empty()) return false; return true; } // function check if a string is more than 50 characters length bool isLargerThan50(int length){ if (length > 50) return false; return true; } // function check if string contains only a and b bool checkLetters(string str, int length){ int i =0; while (i < length) { if(str[i] != 'a' && str[i] !='b' ) return false; i++; } return true; } // function sort a and b string separateLetters(string input){ string temp_a="", temp_b="", sorted_input=""; int i=0; int length = input.length(); while (i < length) { if(input[i] == 'a') temp_a.append("a"); else if(input[i] == 'b') temp_b.append("b"); i++; } sorted_input.append(temp_a); sorted_input.append(temp_b); return sorted_input; } int main() { string input; int length; // ********* READ INPUT *********** cout << "Enter a string: "; getline(cin, input); //find the length of string length = input.length(); // ********* CHECK INPUT ********** // 1. Check the length if it is 50 if (!isLargerThan50(length)){ cout << "\nError -- Length of string is more than 50."; exit (EXIT_FAILURE); } // 2. Check if it is empty if (!isEmpty(input)){ cout << "\nError -- String is empty."; exit (EXIT_FAILURE); } // 3. Check if it contains only a and b if (!checkLetters(input,length)){ cout << "\nError -- String contains characters different than a and b."; exit (EXIT_FAILURE); } // ********* RESULT *********** cout << separateLetters(input); return 0; }

seperateLettersCpp