// Created to show Chriiisss (Discord) how to convert // a string to an integer and produce errors on input // based on our conversation. #include #include int main() { // Read the string containing the integer, default // the integer to zero, remember that no errors // have occurred, unless the string is empty, and // remember the number isn't a negative, until a // minus sign is seen. std::string a; std::cin >> a; long b = 0; bool err = false; if (a.length() == 0) { std::cout << "An integer was expected!" << std::endl; err = true; } bool neg = false; // For each character in the string, process it. for (int i = 0; i < a.length(); i++) // If the character is a digit, process it. if (a[i] >= '0' && a[i] <= '9') { // If the number is going to overflow the 31 // bits allowed for longs, complain, remember // an error occurred, and exit the loop. The // largest valid number is 2,147,484,647 so // if the number is greater than the maximum // 9 digits that can become a 10 digit number // it will overflow. Also, if the 9 digit // number is maxed, but the newest digit is // greater than the allowable 7, it will // overflow. if (b > 214748364 || (a[i] > '7' && b == 214748364)) { std::cout << "Integer is too big" << std::endl; err = true; break; // Otherwise, the number won't overflow so // shift the existing number over and add the // new digit. } else b = b*10+(a[i]-'0'); // Otherwise, if the character is a minus sign in // the first position, remember it occurred. } else if (a[i] == '-' && i == 0) { neg = true; // Otherwise, if the character is not a plus sign // in the first position, the character is invalid // so complain, remember an error occurred, and // exit the loop. } else if (a[i] != '+' || i != 0) { std::cout << "Invalid character in the integer!" << std::endl; err = true; break; } // if // If the number can be negative and it should be, // make it so. if (b > 0 && neg) b = -b; // If the integer is valid, output it. if (!err) std::cout << b << std::endl; return 0; } // main

chriiisss 32bitIntegerRead og