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  1. Recursive Digit Sum
  2. Discussions

Recursive Digit Sum

  • joeljordanjoseph
     + 0 comments

    I really wanted this to work with recursion so I did. After looking here at the comments it seems that multiplying by 'k' after doing the first sum is the best way to optimize away the memory issues. Did this in C++, could be improved upon but i'll settle with this. Also had issues with the way the question was worded, guess I either need to improve my reading comprehension or this needs to be better.

    int superDigit(string n, int k) {
    
    // Base case
    if (n.length() == 1 && k == 0) {
        return std::stoi(n);
    }
    
    // First run
    if (k != 0) {
        size_t sum = 0;        
        for (size_t i = 0; i < n.length(); ++i) {
            sum += n.at(i) - '0';
        }
        sum = sum * k;
        return superDigit(to_string(sum), 0);
        
    } else { // Recursion body
        size_t sum = 0;        
        for (size_t i = 0; i < n.length(); ++i) {
            sum += n.at(i) - '0';
        }

        return superDigit(std::to_string(sum), 0);   
    }
}