Advent of Code 2020: Day 1

p1.cpp

#include <iostream>
#include <string>
#include <sstream>
#include <vector>

int main(int argc, char* argv[])
{
  std::vector<int> expenses;
  std::stringstream ss;

  ss << std::cin.rdbuf();

  for (int n = 0; ss >> n; ) {
    expenses.push_back(n);
  }

  for (int i = 0; i < expenses.size(); i++) {
    int a = expenses[i];

    for (int j = 0; j < expenses.size(); j++) {
      int b = expenses[j];

      if (i != j && a + b == 2020) {
        std::cout << a << " " << b << " " << a * b << std::endl;
        return 0;
      }
    }
  }

  return 0;
}

p1.lua

local expense = {}

for l in io.lines() do
  table.insert(expense, tonumber(l))
end

for _,a in pairs(expense) do
  for _,b in pairs(expense) do
    if a ~= b and a + b == 2020 then
      print(a, b, a * b)
    end
  end
end

p2.cpp

#include <iostream>
#include <string>
#include <sstream>
#include <vector>

int main(int argc, char* argv[])
{
  std::vector<int> expenses;
  std::stringstream ss;

  ss << std::cin.rdbuf();

  for (int n = 0; ss >> n; ) {
    expenses.push_back(n);
  }

  for (int i = 0; i < expenses.size(); i++) {
    int a = expenses[i];

    for (int j = 0; j < expenses.size(); j++) {
      int b = expenses[j];

      for (int k = 0; k < expenses.size(); k++) {
        int c = expenses[k];

        if (i != j && i != k && j != k && a + b + c == 2020) {
          std::cout << a << " " << b << " " << c << " "  << a * b * c << std::endl;
          return 0;
        }
      }
    }
  }

  return 0;
}

p2.lua

local expense = {}

for l in io.lines() do
  table.insert(expense, tonumber(l))
end

for _,a in pairs(expense) do
  for _,b in pairs(expense) do
    for _,c in pairs(expense) do
      if a ~= b and b ~= c and a ~= c and a + b + c == 2020 then
        print(a, b, c, a * b * c)
      end
    end
  end
end