1 files changed, 39 insertions, 0 deletions
diff --git a/src/2017/day5/aoc.cpp b/src/2017/day5/aoc.cpp
index ed2d9d3..a89a18e 100644
--- a/src/2017/day5/aoc.cpp
+++ b/src/2017/day5/aoc.cpp
@@ -1,5 +1,44 @@
 #include "aoc.h"
+#include <vector>
 
 namespace aoc2017 {
 
+int get_number(line_view lv) {
+  const char* p = lv.line;
+  int sign = 1;
+  if (*p == '-') {
+    sign = -1;
+    p++;
+  }
+  int d{0};
+  while (*p >= '0' && *p <= '9') {
+    d = d * 10 + *p - '0';
+    p++;
+  }
+  return d * sign;
 }
+
+void follow(int i, std::vector<int>& ins, int* steps) {
+  // printf("%d\n", ins[i]);
+  int x = ins[i];
+  int n = i + x;
+  if (n >= 0 && n < int(ins.size())) {
+    // ins[i] += x >= 3 ? -1 : 1; part2
+    ins[i] += 1;
+    *steps += 1;
+    follow(n, ins, steps);
+  }
+}
+
+int day5(line_view file) {
+  std::vector<int> ins;
+  per_line(file, [&ins](line_view lv) {
+    ins.emplace_back(get_number(lv));
+    return true;
+  });
+  int steps{0};
+  follow(0, ins, &steps);
+  return steps + 1;
+}
+
+} // namespace aoc2017