Solve problem 6

c++/problem6.cpp

@@ -0,0 +1,37 @@
+#include <algorithm>
+#include <iterator>
+#include <unordered_set>
+#include <set>
+#include "solutions.hpp"
+
+using namespace std;
+
+template <>
+pair<string, string> solve<6>(istream& input) {
+    uint64_t part1 = 0, part2 = 0;
+    unordered_set<char> any_answered;
+    unordered_set<char> all_answered;
+    bool new_group = true;
+    for (string line; getline(input, line); ) {
+        if (!line.empty()) {
+            unordered_set<char> present;
+            for (char c : line) {
+                any_answered.insert(c);
+                if (new_group || all_answered.contains(c)) {
+                    present.insert(c);
+                }
+            }
+            all_answered = present;
+            new_group = false;
+        }
+        if (line.empty() || input.peek() == EOF) {
+            part1 += any_answered.size();
+            part2 += all_answered.size();
+            any_answered.clear();
+            all_answered.clear();
+            new_group = true;
+        }
+    }
+    return pair(to_string(part1), to_string(part2));
+}
+