Add 2016 day 6 puzzles

2016/puzzle-06-02.cc

@@ -0,0 +1,37 @@
+//
+// Created by Matthew Gretton-Dann on 04/12/2021.
+//
+
+#include <algorithm>
+#include <cassert>
+#include <iostream>
+#include <map>
+#include <vector>
+
+auto main() -> int
+{
+  std::vector<std::map<char, unsigned>> counts;
+  std::string line;
+
+  while (std::getline(std::cin, line)) {
+    if (counts.empty()) {
+      counts.resize(line.size());
+    }
+
+    assert(counts.size() == line.size());
+    for (std::size_t i = 0; i < line.size(); ++i) {
+      auto [it, success] = counts[i].insert({line[i], 0});
+      ++(it->second);
+    }
+  }
+
+  for (auto const& idx : counts) {
+    auto letter{std::min_element(idx.begin(), idx.end(), [](auto const& lhs, auto const& rhs) {
+      return lhs.second < rhs.second;
+    })};
+    std::cout << static_cast<char>(letter->first);
+  }
+  std::cout << '\n';
+
+  return 0;
+}