Day 4

d4/main.cxx

@@ -0,0 +1,71 @@
+#include <iostream>
+#include <algorithm>
+#include <numeric>
+#include <fstream>
+#include <sstream>
+#include <string>
+#include <vector>
+#include <regex>
+#include <vector>
+
+struct Card
+{
+  int nr;
+  int gained;
+  std::vector<int> wns;
+  std::vector<int> ns;
+};
+
+int main()
+{
+  std::ifstream file{"../d4/input.txt"};
+  std::string line, ignored;
+  std::vector<Card> cards;
+  constexpr int winningLength{10}, owningLength{25};
+  int sum{0}, nr{0};
+
+  while (std::getline(file, line))
+  {
+    std::stringstream iss(line);
+    std::vector<int> twns, tns;
+    Card c;
+    int n;
+
+    iss >> ignored >> ignored;
+    for (int i{0}; i < winningLength; i++)
+    {
+      iss >> n;
+      twns.emplace_back(n);
+    }
+    iss >> ignored;
+    for (int i{0}; i < owningLength; i++)
+    {
+      iss >> n;
+      tns.emplace_back(n);
+    }
+
+    c.wns = twns;
+    c.ns = tns;
+    c.nr = nr;
+    c.gained = 1;
+    cards.emplace_back(c);
+    nr++;
+  }
+
+  for (const auto &c : cards)
+  {
+    int gainedCards{1};
+    sum += c.gained;
+    for (const auto &n : c.wns)
+    {
+      if (std::find(c.ns.begin(), c.ns.end(), n) != c.ns.end())
+      {
+        cards[c.nr + gainedCards].gained += 1 * c.gained;
+        gainedCards++;
+      }
+    }
+  }
+
+  std::cout << sum << std::endl;
+  return 0;
+}