From dc817bbc9e7ea64763e79dc9c5357a1e64c32dcc Mon Sep 17 00:00:00 2001
From: Eric Mertens <emertens@galois.com>
Date: Wed, 16 Nov 2022 09:18:17 -0800
Subject: [PATCH] tests16

---
 2019/16.cpp | 125 ++++++++++++++++++++++++++++++++++++----------------
 1 file changed, 88 insertions(+), 37 deletions(-)

diff --git a/2019/16.cpp b/2019/16.cpp
index 598fd0b..d515f90 100644
--- a/2019/16.cpp
+++ b/2019/16.cpp
@@ -1,7 +1,10 @@
+#include <cstdint>
 #include <iostream>
 #include <optional>
+#include <sstream>
 #include <vector>
-#include <numeric>
+
+#include <doctest.h>
 
 #include <aocpp/Startup.hpp>
 using namespace aocpp;
@@ -34,44 +37,92 @@ auto FFT(std::size_t const start, std::vector<std::int8_t> const& prev)
   return result;
 }
 
-} // namespace
-
-auto main(int argc, char** argv) -> int {
-  auto & in = aocpp::Startup(argc, argv);
-  std::string input;
-  in >> input;
-
-  std::vector<std::int8_t> signal;
-  for (char const c : input) {
-    signal.push_back(c - '0');
+auto Parse(std::istream & in) -> std::vector<std::int8_t>
+{
+  std::string line;
+  std::getline(in, line);
+  std::vector<std::int8_t> result;
+  result.reserve(line.size());
+  for (auto const c : line) {
+    result.push_back(c - '0');
   }
+  return result;
+}
 
-  for (int i = 0; i < 100; i++) {
-    signal = FFT(0, signal);
-  }
-  for (int i = 0; i < 8; i++) {
-    std::cout << int(signal[i]);
-  }
-  std::cout << std::endl;
-
-  signal.clear();
-  signal.reserve(10000 * input.size());
-  for (int i = 0; i < 10000; i++) {
-    for (char const c : input) {
-      signal.push_back(c - '0');
-    }
-  }
-
-  auto offset = std::stol(input.substr(0,7));
-  std::copy(signal.begin() + offset, signal.end(), signal.begin());
-  signal.resize(signal.size() - offset);
-
-  for (int i = 0; i < 100; i++) {
+auto Compute(
+  std::vector<std::int8_t> signal,
+  std::size_t iterations,
+  std::size_t offset = 0
+) -> std::string
+{
+  for (std::size_t i = 0; i < iterations; i++) {
     signal = FFT(offset, signal);
   }
-
-  for (auto i = 0; i < 8; i++) {
-      std::cout << int(signal[i]);
+  signal.resize(8);
+  std::string result;
+  for (auto const x : signal) {
+    result += char(x + '0');
   }
-  std::cout << std::endl;
-}
\ No newline at end of file
+  return result;
+}
+
+auto Part2(std::vector<int8_t> const& input) -> std::string {
+
+  // Compute offset from first 7 digits of the input
+  std::size_t offset = 0;
+  for (int i = 0; i < 7; i++) {
+    offset = offset * 10 + input[i];
+  }
+
+  // Allocate the storage for 10,000 copies of the input starting at the given offset
+  std::vector<std::int8_t> signal;
+  std::size_t size2 = 10000 * input.size() - offset;
+  signal.reserve(size2);
+
+  // Populate the massively copied signal vector
+  for (std::size_t i = 0, j = offset % input.size(); i < size2; i++) {
+    signal.push_back(input[j++]);
+    if (j == input.size()) j = 0;
+  }
+
+  return Compute(signal, 100, offset);
+}
+
+} // namespace
+
+TEST_SUITE("documented examples") {
+  std::istringstream in;
+  TEST_CASE("part 1") {
+    in = std::istringstream{"12345678"};
+    auto signal = Parse(in);
+    REQUIRE(Compute(signal, 1) == "48226158");
+    REQUIRE(Compute(signal, 2) == "34040438");
+    REQUIRE(Compute(signal, 3) == "03415518");
+    REQUIRE(Compute(signal, 4) == "01029498");
+
+    in = std::istringstream{"80871224585914546619083218645595"};
+    REQUIRE(Compute(Parse(in), 100) == "24176176");
+
+    in = std::istringstream{"19617804207202209144916044189917"};
+    REQUIRE(Compute(Parse(in), 100) == "73745418");
+
+    in = std::istringstream{"69317163492948606335995924319873"};
+    REQUIRE(Compute(Parse(in), 100) == "52432133");
+  }
+
+  TEST_CASE("part 2") {
+    in = std::istringstream{"03036732577212944063491565474664"};
+    REQUIRE(Part2(Parse(in)) == "84462026");
+    in = std::istringstream{"02935109699940807407585447034323"};
+    REQUIRE(Part2(Parse(in)) == "78725270");
+    in = std::istringstream{"03081770884921959731165446850517"};
+    REQUIRE(Part2(Parse(in)) == "53553731");
+  }
+}
+
+auto main(int argc, char** argv) -> int {
+  auto input = Parse(aocpp::Startup(argc, argv));
+
+  std::cout << "Part 1: " << Compute(input, 100, 0) << std::endl;
+  std::cout << "Part 2: " << Part2(input) << std::endl;
+}