Add 2021 solutions

src/2021/Day08.cpp

@@ -0,0 +1,154 @@
+#include "common/aoc.h"
+
+namespace y2021::day08
+{
+  struct Signal
+  {
+    std::vector<std::set<char>> numbers;
+    std::vector<std::set<char>> display;
+  };
+
+  REGISTER_DAY(2021, Day08, std::vector<Signal>, int);
+
+  REGISTER_TEST_EXAMPLE(2021, Day08, ExampleInput, 1, 26);
+  REGISTER_TEST(2021, Day08, Input, 1, 301);
+  REGISTER_TEST_EXAMPLE(2021, Day08, ExampleInput, 2, 61229);
+  REGISTER_TEST(2021, Day08, Input, 2, 908067);
+
+  READ_INPUT(input)
+  {
+    std::string str;
+    std::vector<Signal> signals;
+    while (getline(input, str))
+    {
+      Signal signal;
+      std::stringstream ss{str};
+      for (int i = 0; i < 10; i++)
+      {
+        std::string s;
+        ss >> s;
+        std::set<char> set;
+        for (char c : s) set.emplace(c);
+        signal.numbers.emplace_back(set);
+      }
+      char c;
+      ss >> c;
+      for (int i = 0; i < 4; i++)
+      {
+        std::string s;
+        ss >> s;
+        std::set<char> set;
+        for (char c : s) set.emplace(c);
+        signal.display.emplace_back(set);
+      }
+      signals.emplace_back(signal);
+    }
+    return signals;
+  }
+
+  OUTPUT1(input)
+  {
+    int count = 0;
+    for (auto&& signal : input)
+    {
+      for (auto&& number : signal.display)
+      {
+        if (number.size() == 2 || number.size() == 3 || number.size() == 4 || number.size() == 7)
+          count++;
+      }
+    }
+    return count;
+  }
+
+  OUTPUT2(input)
+  {
+    int sum = 0;
+    for (auto&& signal : input)
+    {
+      std::vector<std::set<char>> numbers(10);
+      // Find all numbers with unique amount of segments
+      for (auto&& number : signal.numbers)
+      {
+        if (number.size() == 2)
+          numbers[1] = number;
+        if (number.size() == 3)
+          numbers[7] = number;
+        if (number.size() == 4)
+          numbers[4] = number;
+        if (number.size() == 7)
+          numbers[8] = number;
+      }
+
+      // Find all numbers with five and six segments
+      std::vector<std::set<char>> fivesegs;
+      std::vector<std::set<char>> sixsegs;
+      for (auto&& number : signal.numbers)
+      {
+        if (number.size() == 5)
+          fivesegs.emplace_back(number);
+        if (number.size() == 6)
+          sixsegs.emplace_back(number);
+      }
+
+      // Find number 3 (only five segment number which 1 is a subset of)
+      for (auto it = fivesegs.begin(); it != fivesegs.end(); it++)
+      {
+        if (Helper::IsSubset(numbers[1], *it))
+        {
+          numbers[3] = *it;
+          fivesegs.erase(it);
+          break;
+        }
+      }
+
+      // Find number 6 (only six segment number which is not a subset of 1)
+      for (auto it = sixsegs.begin(); it != sixsegs.end(); it++)
+      {
+        if (!Helper::IsSubset(numbers[1], *it))
+        {
+          numbers[6] = *it;
+          sixsegs.erase(it);
+          break;
+        }
+      }
+
+      // Find number 5 (only five segment number which is a subset of 6)
+      for (auto it = fivesegs.begin(); it != fivesegs.end(); it++)
+      {
+        if (Helper::IsSubset(*it, numbers[6]))
+        {
+          numbers[5] = *it;
+          fivesegs.erase(it);
+          break;
+        }
+      }
+      // Find number 2 (last five segment number)
+      numbers[2] = fivesegs.front();
+
+      // Find number 9 (only six segment number which 4 is a subset of)
+      for (auto it = sixsegs.begin(); it != sixsegs.end(); it++)
+      {
+        if (Helper::IsSubset(numbers[4], *it))
+        {
+          numbers[9] = *it;
+          sixsegs.erase(it);
+          break;
+        }
+      }
+
+      // Find number 0 (last six segment number)
+      numbers[0] = sixsegs.front();
+
+      // Calculate the segment display
+      int num = 0;
+      for (auto number : signal.display)
+      {
+        auto it = std::find(numbers.begin(), numbers.end(), number);
+        int i = it - numbers.begin();
+        num = num * 10 + i;
+      }
+      sum += num;
+    }
+    return sum;
+  }
+}