Long Encoded String

long-encoded-string.cc

#include <iostream>
#include <regex>

using namespace std;

int alphabet[26];

void tokenized(int a, int c) {
    alphabet[a - 1] += c;
}

int main() {
    // inputs for encoded-string
    string s;
    cin >> s;

    // check valid string
    regex r("[0-9#()]*");
    if (!(regex_match(s.begin(), s.end(), r))) {
        cout << "Error" << endl;
        return 0;
    }

    // insert meaningless char for comparison conveniently.
    s[s.size()] = '-';
    s[s.size()] = '-';
    s[s.size()] = '-';

    // tokenizing
    int a = 0, c = 0;
    bool c_tag_opened = false;

    for (int i = 0; i < s.size(); i++) {
        switch (s[i]) {
            case '(':
                c_tag_opened = true;
                break;
            case ')':
                c_tag_opened = false;
                tokenized(a, c);
                c = 0;
                break;
            default:
                if (c_tag_opened) {
                    c = c * 10 + (s[i] - '0'); // be careful, max count is 99
                } else {
                    if (s[i + 2] != '#') { // single num
                        a = s[i] - '0'; // https://stackoverflow.com/a/5030086/3513266
                        if (s[i + 1] != '(') {
                            tokenized(a, 1);
                        }
                    } else if (s[i + 2] == '#') { // double num
                        a = (s[i] - '0') * 10 + (s[i + 1] - '0');

                        if (s[i + 3] != '(') {
                            tokenized(a, 1);
                        }
                        i += 2; // skip double number
                    }
                }
                break;
        }
    }

    // print an array
    for (int i = 0; i < 26; i++)
        cout << alphabet[i] << " ";
    cout << endl;

    return 0;
}