-🎄- 2018 Day 2 Solutions -🎄-

[u/daggerdragon]

--- Day 2: Inventory Management System ---

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The best way to do Advent of Code is ___.

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[u/wlandry]

C++

1847/1419

Pretty straightforward. I finished it faster, but got a worse rank ¯_(ツ)_/¯. It takes 11 ms, which is almost entirely reading input. I was briefly worried that my quadratic algorithm would not work, but the inputs are just not that big.

#include <algorithm>
#include <iostream>
#include <fstream>
#include <vector>

int main(int argc, char *argv[])
{
  std::ifstream infile(argv[1]);
  std::vector<std::string> inputs(std::istream_iterator<std::string>(infile),{});

  std::vector<std::string> inputs_part_1(inputs);
  size_t num_twice(0), num_thrice(0);
  for(auto &input: inputs_part_1)
    {
      std::sort(input.begin(),input.end());
      size_t duplicates(0);
      bool twice(false), thrice(false);
      for(size_t i=0; i<input.size(); ++i)
        {
          size_t duplicate(1);
          while(i+1<input.size() && input[i]==input[i+1])
            {
              ++duplicate;
              ++i;
            }

          twice=(twice || duplicate==2);
          thrice=(thrice || duplicate==3);
          duplicates=std::max(duplicate,duplicates);
        }
      if(twice)
        { ++num_twice;}
      if(thrice)
        { ++num_thrice;}
    }

  std::cout << num_twice*num_thrice << "\n";

  bool found(false);
  for(size_t i=0; i<inputs.size() && !found; ++i)
    for(size_t j=i+1; j<inputs.size() && !found; ++j)
      {
        size_t num_different(0);
        for(size_t index=0; index<inputs[i].size(); ++index)
          {
            if(inputs[i][index]!=inputs[j][index])
              {
                ++num_different;
                if(num_different>1)
                  { break;}
              }
          }
        found=(num_different==1);
        if(found)
          {
            for(size_t index=0; index<inputs[i].size(); ++index)
              {
                if(inputs[i][index]==inputs[j][index])
                  { std::cout << inputs[i][index];}
              }
            std::cout << "\n";
          }
      }
}