From db6c4680263981594cacd464e4abfea38586b9d5 Mon Sep 17 00:00:00 2001
From: kaiwu <kaiwu2004@gmail.com>
Date: Mon, 4 Apr 2022 10:55:15 +0800
Subject: 2018 day1

---
 src/2018/day1/aoc.cpp | 42 +++++++++++++++++++++++++++++++++++++++++-
 1 file changed, 41 insertions(+), 1 deletion(-)

(limited to 'src/2018/day1/aoc.cpp')

diff --git a/src/2018/day1/aoc.cpp b/src/2018/day1/aoc.cpp
index 1d092ff..aea1e97 100644
--- a/src/2018/day1/aoc.cpp
+++ b/src/2018/day1/aoc.cpp
@@ -1,3 +1,43 @@
 #include "aoc.h"
+#include <set>
 
-namespace aoc2018 {}
+namespace aoc2018 {
+int parse_day1(line_view lv) {
+  const char* p = lv.line;
+  int sign = *p++ == '+' ? 1 : -1;
+  int s{0};
+  while (*p >= '0' && *p <= '9') {
+    s = s * 10 + *p - '0';
+    p++;
+  }
+  return sign * s;
+}
+
+int day1(line_view file) {
+  int sum{0};
+
+  per_line(file, [&sum](line_view lv) {
+    sum += parse_day1(lv);
+    return true;
+  });
+  return sum;
+}
+
+int day1part2(line_view file) {
+  std::set<int> frequencies;
+
+  int f{0};
+  bool found{false};
+  while (!found) {
+    per_line(file, [&f, &frequencies, &found](line_view lv) {
+      f += parse_day1(lv);
+      // printf("%d\n", f);
+      auto p = frequencies.insert(f);
+      found = !p.second;
+      return p.second;
+    });
+  }
+  return f;
+}
+
+} // namespace aoc2018
-- 
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