1 files changed, 56 insertions, 0 deletions
diff --git a/src/2018/day2/aoc.cpp b/src/2018/day2/aoc.cpp
index 585f144..fd7e8e6 100644
--- a/src/2018/day2/aoc.cpp
+++ b/src/2018/day2/aoc.cpp
@@ -1,5 +1,61 @@
 #include "aoc.h"
+#include <vector>
 
 namespace aoc2018 {
 
+int exactly(const ascii_count& ac, int x) {
+  for (char i = 'a'; i <= 'z'; i++) {
+    if (ac.count[int(i)] == x) {
+      return 1;
+    }
+  }
+  return 0;
 }
+
+bool almost(line_view lv1, line_view lv2, char comm[]) {
+  const char* p1 = lv1.line;
+  const char* p2 = lv2.line;
+  int x{0};
+  int i{0};
+  while (p1 < lv1.line + lv1.length - 1 && x < 2) {
+    if (*p1 == *p2) {
+      comm[i++] = *p1;
+    } else {
+      x++;
+    }
+    p1++;
+    p2++;
+  }
+  return x == 1;
+}
+
+void diff(size_t i, const std::vector<line_view>& ls, char comm[]) {
+  if (i < ls.size() - 1) {
+    for (size_t j = i + 1; j < ls.size(); j++) {
+      if (almost(ls[i], ls[j], comm)) {
+        return;
+      }
+    }
+    diff(i + 1, ls, comm);
+  }
+}
+
+int day2(line_view file, char comm[]) {
+  int exactly2{0};
+  int exactly3{0};
+  std::vector<line_view> ls;
+
+  per_line(file, [&exactly2, &exactly3, &ls](line_view lv) {
+    ls.push_back(lv);
+    ascii_count ac(lv);
+    exactly2 += exactly(ac, 2);
+    exactly3 += exactly(ac, 3);
+    return true;
+  });
+
+  diff(0, ls, comm);
+
+  return exactly2 * exactly3;
+}
+
+} // namespace aoc2018