2021 day6 part1

1 files changed, 47 insertions, 0 deletions

diff --git a/src/2021/day6/aoc.cpp b/src/2021/day6/aoc.cpp
index 7a3c895..98ece02 100644
--- a/src/2021/day6/aoc.cpp
+++ b/src/2021/day6/aoc.cpp
@@ -1,5 +1,52 @@
 #include "aoc.h"
+#include <algorithm>
+#include <vector>
 
 namespace aoc2021 {
 
+static void run(int day, std::vector<int>& v) {
+  // std::for_each(v.begin(), v.end(), [](int i) { printf("%d ", i); });
+  // printf(": %zu\n", v.size());
+  if (day > 0) {
+    int count{0};
+    for (auto& i : v) {
+      if (i > 0) {
+        i--;
+      } else {
+        i = 6;
+        count += 1;
+      }
+    }
+    while (count > 0) {
+      v.push_back(8);
+      count--;
+    }
+    run(day - 1, v);
+  }
 }
+
+size_t day6(int i, int days) {
+  std::vector<int> v = {i};
+  run(days, v);
+  return v.size();
+}
+
+size_t day6(line_view file, int days) {
+  size_t ns[7] = {0};
+  for (int i : {0, 1, 2, 3, 4, 5, 6}) {
+    ns[i] = day6(i, days);
+    printf("--> %d : %zu\n", i, ns[i]);
+  }
+
+  size_t total{0};
+  const char* p = file.line;
+  while (p < file.line + file.length) {
+    if (*p >= '0' && *p <= '9') {
+      total += ns[*p - '0'];
+    }
+    p++;
+  }
+  return total;
+}
+
+} // namespace aoc2021