2021 day7 part1

1 files changed, 50 insertions, 0 deletions

diff --git a/src/2021/day7/aoc.cpp b/src/2021/day7/aoc.cpp
index f01daef..6ba7c29 100644
--- a/src/2021/day7/aoc.cpp
+++ b/src/2021/day7/aoc.cpp
@@ -1,4 +1,54 @@
 #include "aoc.h"
+#include <map>
 
 namespace aoc2021 {
+static void get_number(const char** pp, int* d) {
+  const char* p = *pp;
+  *d = 0;
+  while (*p >= '0' && *p <= '9') {
+    *d = *d * 10 + *p - '0';
+    p++;
+  }
+  *pp = p;
 }
+
+int fuel(int a, const std::map<int, int>& is) {
+  int total{0};
+  for (auto& kv : is) {
+    if (kv.first != a) {
+      total += std::abs(a - kv.first) * kv.second;
+    }
+  }
+  return total;
+}
+
+int day7(line_view file) {
+  std::map<int, int> is;
+  const char* p1 = file.line;
+  const char* p2 = p1 + file.length;
+  int mi{INT32_MAX};
+  int mx{INT32_MIN};
+  while (p1 < p2) {
+    if (*p1 >= '0' && *p1 <= '9') {
+      int d{0};
+      get_number(&p1, &d);
+      mi = std::min(mi, d);
+      mx = std::max(mx, d);
+      is[d] += 1;
+    }
+    p1++;
+  }
+
+  int min{INT32_MAX};
+  for (int i = mi; i <= mx; i++) {
+    int f = fuel(i, is);
+    // printf("%d -> %d\n", i, f);
+    if (f < min) {
+      min = f;
+    }
+  }
+
+  return min;
+}
+
+} // namespace aoc2021