Initial commit

2015/puzzle-05-02.cc

@@ -0,0 +1,45 @@
+#include <algorithm>
+#include <cassert>
+#include <iostream>
+#include <set>
+#include <string>
+
+// Check if a string is nice:
+// Nice strings have:
+//   repeated double letters - but not overlapping
+//   repeated letters separated by one other.
+bool is_nice(std::string const &s) noexcept {
+  bool repeated_pair = false;
+  bool repeated_sep = false;
+
+  std::cout << s;
+  for (std::string::size_type i = 0; i < s.length() - 2; ++i) {
+    // Find whether the two characters starting at i are repeated in the rest of
+    // the string.  We don't have to look backwards as we will already have
+    // scanned it.
+    if (s.substr(i + 2).find(s.substr(i, 2)) != std::string::npos) {
+      repeated_pair = true;
+      std::cout << " repeated(" << s.substr(i, 2) << ")";
+    }
+    if (s[i] == s[i + 2]) {
+      repeated_sep = true;
+      std::cout << " pair(" << s.substr(i, 3) << ")";
+    }
+  }
+  if (repeated_pair && repeated_sep) {
+    std::cout << " match";
+  }
+  std::cout << "\n";
+
+  return repeated_pair && repeated_sep;
+}
+
+int main(int argc, char **argv) {
+  unsigned nice_strings;
+  for (std::string line; std::getline(std::cin, line);) {
+    nice_strings += is_nice(line);
+  }
+  std::cout << nice_strings << '\n';
+
+  return 0;
+}