//input expression like : 965194561616165-65162132162165465165+51616461516546512-99 #include #include #include std::string result; inline std::string find_sum(char a, char b) { return std::to_string(a + b - 2 * '0'); } inline char find_sub(char a, char b) { return char(a - b + '0'); } void add_one(std::string& s, int len) { if (s[len] == '9') { if (len - 1 != -1) { s[len] = '0'; add_one(s, len - 1); } else s = "1" + s; } else s[len]++; } void take_borrow(std::string& s, int len) { if (s[len] == '0') { s[len] = '9'; take_borrow(s, len - 1); } else s[len]--; } std::string& add(std::string& num1, std::string& num2) { num1 = "0" + num1; num2 = "0" + num2; //storing length: int len1 = num1.length(); int len2 = num2.length(); //calculating sum while (len1 != 0 && len2 != 0) { std::string res = find_sum(num1[--len1], num2[--len2]); if (res.length() == 2) { (len1 > len2) ? add_one(num1, len1 - 1) : add_one(num2, len2 - 1); result = res[1] + result; } else result = res + result; } while (len1 != 0) result = num1[--len1] + result; while (len2 != 0) result = num2[--len2] + result; //printing answer. if (result[0] == '0') result.erase(result.begin()); return result; //std::cout << result << '\n'; } std::string& sub(std::string& num1, std::string& num2) { int len1 = num1.length(); int len2 = num2.length(); while (len2 != 0) { if (num1[--len1] >= num2[--len2]) result = find_sub(num1[len1], num2[len2]) + result; else { take_borrow(num1, len1 - 1); result = char('9' + 1 + num1[len1] - num2[len2]) + result; } } while (len1 != 0) result = num1[--len1] + result; return result; } void make_num1_max(std::string& num1, std::string& num2) { int len1 = (num1[0] == '-' ? num1.length() - 1 : num1.length()); int len2 = (num1.length() == len1 ? num2.length() - 1 : num2.length()); if (len1 > len2) return; else if (len2 > len1) num1.swap(num2); else { int i = 0, j = 0; num1[0] == '-' ? i = 1 : j = 1; for (int k = 0; k < len1; k++) if (num1[k + i]>num2[j + k]) return; else if (num1[k + i] < num2[j + k]) { num1.swap(num2); return; } } } void perform_operation(std::string& num1, std::string& num2) { result = ""; bool is_result_negative = false; if (num1[0] == '-' && num2[0] == '-') { is_result_negative = true; num1.erase(num1.begin()); num2.erase(num2.begin()); add(num1,num2); } else if (num1[0] != '-' && num2[0] != '-') add(num1,num2); else { make_num1_max(num1, num2); if (num1[0] == '-') { num1.erase(num1.begin()); is_result_negative = true; } if (num2[0] == '-') num2.erase(num2.begin()); sub(num1,num2); } if (is_result_negative) result = "-" + result; } std::string get_num(std::string& input) { static int i = 0; if (i == input.length()) return std::string(""); if (input[i] == '+') i++; int start = i; if (input[i] == '-') i++; for (; i != input.length(); i++) { if (input[i] == '+' || input[i] == '-') break; } return input.substr(start, i-start); } void remove_zeros(std::string& num) { int offset = (num[0] == '-' ? 1 : 0); while (num[0 + offset] == '0') num.erase(num.begin() + offset); } int main() { std::string num1, num2; std::string input="965194561616165-65162132162165465165+51616461516546512-99"; std::cin >> input; std::cout << "input : " << input << std::endl; std::regex valid_exp("((\\+|-)?[[:digit:]])*"); if (!std::regex_match(input, valid_exp)) { std::cout << "Not a valid expression."; system("pause"); return 0; } remove_zeros(num1 = get_num(input)); remove_zeros(num2 = get_num(input)); perform_operation(num1,num2); while ((num2 = get_num(input)) != std::string("")) { remove_zeros(num2); num1 = result; perform_operation(num1, num2); } remove_zeros(result); std::cout << "\nresult : "; if (result.length() == 0) std::cout << "0"; std::cout << result << std::endl; }

Big Number addition subtraction