day1

3 files changed, 42 insertions, 1 deletions

diff --git a/src/2015/day1/README.md b/src/2015/day1/README.md
index 98b59a6..cf9151a 100644
--- a/src/2015/day1/README.md
+++ b/src/2015/day1/README.md
@@ -22,3 +22,14 @@ For example:
 
 To what floor do the instructions take Santa?
 
+--- Part Two ---
+
+Now, given the same instructions, find the position of the first character that causes him to enter the basement (floor -1). The first character in the instructions has position 1, the second character has position 2, and so on.
+
+For example:
+
+    ) causes him to enter the basement at character position 1.
+    ()()) causes him to enter the basement at character position 5.
+
+What is the position of the character that causes Santa to first enter the basement?
+
diff --git a/src/2015/day1/aoc.cpp b/src/2015/day1/aoc.cpp
index 2263558..4a4d4fc 100644
--- a/src/2015/day1/aoc.cpp
+++ b/src/2015/day1/aoc.cpp
@@ -5,9 +5,38 @@ namespace aoc2015 {
 int day1(line_view lv) {
   int level = 0;
   for (size_t i = 0; i < lv.length; ++i) {
-    level += lv.line[i] == '(' ? 1 : -1;
+    switch (lv.line[i]) {
+    case '(':
+      level += 1;
+      break;
+    case ')':
+      level += -1;
+      break;
+    default:
+      break;
+    }
   }
   return level;
 }
 
+int day1(line_view lv, int target) {
+  int level = 0;
+  for (size_t i = 0; i < lv.length; ++i) {
+    switch (lv.line[i]) {
+    case '(':
+      level += 1;
+      break;
+    case ')':
+      level += -1;
+      break;
+    default:
+      break;
+    }
+    if (level == target) {
+      return i + 1;
+    }
+  }
+  return -1;
+}
+
 } // namespace aoc2015
diff --git a/src/2015/day1/aoc.h b/src/2015/day1/aoc.h
index b83b525..af68f6a 100644
--- a/src/2015/day1/aoc.h
+++ b/src/2015/day1/aoc.h
@@ -5,5 +5,6 @@
 namespace aoc2015 {
 
 int day1(line_view lv);
+int day1(line_view lv, int target);
 
 }