2017 day4

1 files changed, 77 insertions, 0 deletions

diff --git a/src/2017/day4/aoc.cpp b/src/2017/day4/aoc.cpp
index ed2d9d3..9892b4b 100644
--- a/src/2017/day4/aoc.cpp
+++ b/src/2017/day4/aoc.cpp
@@ -1,5 +1,82 @@
 #include "aoc.h"
+#include <vector>
 
 namespace aoc2017 {
 
+typedef bool (*match_f)(const char*, const char*);
+bool match(const char* p1, const char* p2) {
+  auto is_az = [](char c) { return c >= 'a' && c <= 'z'; };
+  while (is_az(*p1) && is_az(*p2)) {
+    if (*p1++ != *p2++) {
+      return false;
+    }
+  }
+  return !is_az(*p1) && !is_az(*p2);
 }
+
+bool anagram(const char* p1, const char* p2) {
+  auto is_az = [](char c) { return c >= 'a' && c <= 'z'; };
+  auto len = [&is_az](const char* p, int is[]) {
+    const char* p0 = p;
+    while (is_az(*p)) {
+      is[int(*p - 'a')]++;
+      p++;
+    }
+    return p - p0;
+  };
+  int is1[26] = {0};
+  int is2[26] = {0};
+  int l1 = len(p1, is1);
+  int l2 = len(p2, is2);
+  if (l1 != l2) {
+    return false;
+  }
+  for (int i = 0; i < 26; i++) {
+    if (is1[i] != is2[i]) {
+      return false;
+    }
+  }
+  return true;
+}
+
+bool compare(size_t i, const std::vector<const char*>& ps, match_f f) {
+  if (i < ps.size() - 1) {
+    for (size_t j = i + 1; j < ps.size(); j++) {
+      if (f(ps[i], ps[j])) {
+        return false;
+      }
+    }
+    return compare(i + 1, ps, f);
+  }
+  return true;
+}
+
+bool is_valid(line_view lv, match_f f) {
+  const char* p = lv.line;
+  std::vector<const char*> ps;
+  ps.push_back(p);
+  while (p < lv.line + lv.length) {
+    if (*p == ' ') {
+      ps.push_back(p + 1);
+    }
+    p++;
+  }
+  return compare(0, ps, f);
+}
+
+std::pair<int, int> day4(line_view file) {
+  int t0{0};
+  int t1{0};
+  per_line(file, [&t0, &t1](line_view lv) {
+    if (is_valid(lv, match)) {
+      t0 += 1;
+    }
+    if (is_valid(lv, anagram)) {
+      t1 += 1;
+    }
+    return true;
+  });
+  return {t0, t1};
+}
+
+} // namespace aoc2017