2020 day2

1 files changed, 54 insertions, 0 deletions

diff --git a/src/2020/day2/aoc.cpp b/src/2020/day2/aoc.cpp
index 849bad9..cc95f26 100644
--- a/src/2020/day2/aoc.cpp
+++ b/src/2020/day2/aoc.cpp
@@ -2,4 +2,58 @@
 
 namespace aoc2020 {
 
+int count(char c, const char* p) {
+  int total{0};
+  while (*p >= 'a' && *p <= 'z') {
+    if (*p == c) {
+      total++;
+    }
+    p++;
+  }
+  return total;
 }
+
+void minmax(int* min, int* max, const char* p1, const char* p2) {
+  int* p = min;
+  while (p1 < p2) {
+    if (*p1 >= '0' && *p1 <= '9') {
+      *p = *p * 10 + *p1 - '0';
+    } else {
+      p = max;
+    }
+    p1++;
+  }
+}
+
+// 8-10 g: gggggggggg
+bool is_valid1(line_view lv) {
+  const char* p = lv.contains(":");
+  int n = count(*(p - 1), p + 2);
+  int min{0};
+  int max{0};
+  minmax(&min, &max, lv.line, p - 2);
+  return n >= min && n <= max;
+}
+
+bool is_valid2(line_view lv) {
+  const char* p = lv.contains(":");
+  int p1{0};
+  int p2{0};
+  minmax(&p1, &p2, lv.line, p - 2);
+  bool b1 = *(p + 1 + p1) == *(p - 1);
+  bool b2 = *(p + 1 + p2) == *(p - 1);
+  return int(b1) + int(b2) == 1;
+}
+
+std::pair<int, int> day2(line_view file) {
+  int total0{0};
+  int total1{0};
+  per_line(file, [&total0, &total1](line_view lv) {
+    total0 += int(is_valid1(lv));
+    total1 += int(is_valid2(lv));
+    return true;
+  });
+  return {total0, total1};
+}
+
+} // namespace aoc2020