2021 day1

1 files changed, 48 insertions, 1 deletions

diff --git a/src/2021/day1/aoc.cpp b/src/2021/day1/aoc.cpp
index 5f8b1ce..2abe76e 100644
--- a/src/2021/day1/aoc.cpp
+++ b/src/2021/day1/aoc.cpp
@@ -1,3 +1,50 @@
 #include "aoc.h"
+#include <algorithm>
+#include <vector>
 
-namespace aoc2021 {}
+namespace aoc2021 {
+
+int get_number(const char* p) {
+  int d{0};
+  while (*p >= '0' && *p <= '9') {
+    d = d * 10 + *p - '0';
+    p++;
+  }
+  return d;
+}
+
+int increase_1(const std::vector<int>& is) {
+  int total{0};
+  int last{0};
+  std::for_each(is.begin(), is.end(), [&total, &last](int d) {
+    total += (last != 0 && d > last) ? 1 : 0;
+    last = d;
+    return true;
+  });
+  return total;
+}
+
+int increase_3(const std::vector<int>& is) {
+  int total{0};
+  auto sum3 = [](const int* is) { return *is + *(is + 1) + *(is + 2); };
+  const int* p1 = is.data();
+  const int* p2 = p1 + is.size() - 3;
+  while (p1 < p2) {
+    if (sum3(p1 + 1) > sum3(p1)) {
+      total += 1;
+    }
+    p1++;
+  }
+  return total;
+}
+
+std::pair<int, int> day1(line_view file) {
+  std::vector<int> is;
+  per_line(file, [&is](line_view lv) {
+    is.emplace_back(get_number(lv.line));
+    return true;
+  });
+  return {increase_1(is), increase_3(is)};
+}
+
+} // namespace aoc2021