2019 day2 part1

1 files changed, 46 insertions, 0 deletions

diff --git a/src/2019/day2/aoc.cpp b/src/2019/day2/aoc.cpp
index f0cbc1b..7707191 100644
--- a/src/2019/day2/aoc.cpp
+++ b/src/2019/day2/aoc.cpp
@@ -1,5 +1,51 @@
 #include "aoc.h"
+#include <vector>
 
 namespace aoc2019 {
 
+int get_number(const char** pp) {
+  const char* p = *pp;
+  int d{0};
+  while (*p >= '0' && *p <= '9') {
+    d = d * 10 + *p - '0';
+    p++;
+  }
+  *pp = p;
+  return d;
 }
+
+void run(size_t i, std::vector<int>& codes) {
+  // printf("execute %d at %zu\n", codes[i], i);
+  switch (codes[i]) {
+  case 1:
+    codes[codes[i + 3]] = codes[codes[i + 1]] + codes[codes[i + 2]];
+    run(i + 4, codes);
+    break;
+  case 2:
+    codes[codes[i + 3]] = codes[codes[i + 1]] * codes[codes[i + 2]];
+    run(i + 4, codes);
+    break;
+  case 99:
+    break;
+  default:
+    printf("UNKNOWN CODE %d at %zu\n", codes[i], i);
+    break;
+  }
+}
+
+int day2(line_view file) {
+  std::vector<int> optcodes;
+  const char* p = file.line;
+  while (p < file.line + file.length) {
+    if (*p >= '0' && *p <= '9') {
+      optcodes.emplace_back(get_number(&p));
+    }
+    p++;
+  }
+  optcodes[1] = 12;
+  optcodes[2] = 2;
+  run(0, optcodes);
+  return optcodes[0];
+}
+
+} // namespace aoc2019