1 files changed, 85 insertions, 0 deletions
diff --git a/src/2017/day8/aoc.cpp b/src/2017/day8/aoc.cpp
index ed2d9d3..a5af770 100644
--- a/src/2017/day8/aoc.cpp
+++ b/src/2017/day8/aoc.cpp
@@ -1,5 +1,90 @@
 #include "aoc.h"
+#include <unordered_map>
 
 namespace aoc2017 {
 
+int largest(const std::unordered_map<line_view, int>& rs) {
+  int max{INT32_MIN};
+  for (auto& kv : rs) {
+    if (kv.second > max) {
+      max = kv.second;
+    }
+  }
+  return max;
 }
+
+static void get_number(const char** pp, int* d) {
+  const char* p = *pp;
+  *d = 0;
+  int sign = 1;
+  if (*p == '-') {
+    sign = -1;
+    p++;
+  }
+  while (*p >= '0' && *p <= '9') {
+    *d = *d * 10 + *p - '0';
+    p++;
+  }
+  *d = *d * sign;
+  *pp = p;
+}
+
+line_view get_label(const char** pp) {
+  const char* p = *pp;
+  const char* p1 = p;
+  while (*p != ' ') {
+    p++;
+  }
+  *pp = p;
+  return {p1, p};
+}
+
+static int inc(int x, int i) { return x + i; }
+static int dec(int x, int i) { return x - i; }
+static bool condition_met(line_view cond, int x, int i) {
+  if (cond.length > 1) {
+    if (*cond.line == '!') {
+      return x != i;
+    }
+    if (*cond.line == '=') {
+      return x == i;
+    }
+    return (*cond.line == '>') ? x >= i : x <= i;
+  }
+  return (*cond.line == '>') ? x > i : x < i;
+}
+
+typedef int (*op)(int, int);
+std::pair<int, int> day8(line_view file) {
+  std::unordered_map<line_view, int> registers;
+  int max{INT32_MIN};
+  per_line(file, [&registers, &max](line_view lv) {
+    const char* p = lv.line;
+    line_view v1 = get_label(&p);
+    op f = p[1] == 'd' ? dec : inc;
+
+    p += 5;
+    int d1{0};
+    get_number(&p, &d1);
+
+    p += 4;
+    line_view v2 = get_label(&p);
+
+    p += 1;
+    line_view condition = get_label(&p);
+
+    p += 1;
+    int d2{0};
+    get_number(&p, &d2);
+    if (condition_met(condition, registers[v2], d2)) {
+      registers[v1] = f(registers[v1], d1);
+      if (registers[v1] > max) {
+        max = registers[v1];
+      }
+    }
+    return true;
+  });
+  return {largest(registers), max};
+}
+
+} // namespace aoc2017