3 files changed, 46 insertions, 0 deletions
diff --git a/src/2015/day12/README.md b/src/2015/day12/README.md
index 0784931..f242cd3 100644
--- a/src/2015/day12/README.md
+++ b/src/2015/day12/README.md
@@ -15,4 +15,13 @@ You will not encounter any strings containing numbers.
 
 What is the sum of all numbers in the document?
 
+--- Part Two ---
 
+Uh oh - the Accounting-Elves have realized that they double-counted everything red.
+
+Ignore any object (and all of its children) which has any property with the value "red". Do this only for objects ({...}), not arrays ([...]).
+
+    [1,2,3] still has a sum of 6.
+    [1,{"c":"red","b":2},3] now has a sum of 4, because the middle object is ignored.
+    {"d":"red","e":[1,2,3,4],"f":5} now has a sum of 0, because the entire structure is ignored.
+    [1,"red",5] has a sum of 6, because "red" in an array has no effect.
diff --git a/src/2015/day12/aoc.cpp b/src/2015/day12/aoc.cpp
index 1c33c66..3b1ed2b 100644
--- a/src/2015/day12/aoc.cpp
+++ b/src/2015/day12/aoc.cpp
@@ -2,4 +2,39 @@
 
 namespace aoc2015 {
 
+int parse_day12(const char* p1, const char* p2) {
+  int sign = *(p1 - 1) == '-' ? -1 : 1;
+  int d{0};
+  while (p1 != p2) {
+    d = d * 10 + *p1 - '0';
+    p1++;
+  }
+  return sign * d;
 }
+
+int day12(line_view file) {
+  int total = 0;
+  const char* p1 = file.line;
+  const char* p2 = p1;
+  bool to_parse = false;
+  while (p2 < file.line + file.length) {
+    if (*p2 >= '0' && *p2 <= '9') {
+      if (!to_parse) {
+        p1 = p2;
+        to_parse = !to_parse;
+      }
+    } else {
+      if (to_parse) {
+        total += parse_day12(p1, p2);
+        to_parse = !to_parse;
+      }
+    }
+    p2++;
+  }
+  if (to_parse) {
+    total += parse_day12(p1, p2);
+  }
+  return total;
+}
+
+} // namespace aoc2015
diff --git a/src/2015/day12/aoc.h b/src/2015/day12/aoc.h
index c439c03..66d7164 100644
--- a/src/2015/day12/aoc.h
+++ b/src/2015/day12/aoc.h
@@ -3,4 +3,6 @@
 
 namespace aoc2015 {
 
+int day12(line_view file);
+
 }