Day 11

Author: bt

CMakeLists.txt

@@ -7,7 +7,6 @@ add_compile_options(-Wall -Wextra -Wpedantic -O2)
 function(add_challenge name)
     add_executable(${name} ${CMAKE_CURRENT_SOURCE_DIR}/src/${name}.cpp)
     target_include_directories(${name} PRIVATE ${CMAKE_SOURCE_DIR}/include)
-    target_include_directories(${name} PRIVATE ${CMAKE_SOURCE_DIR}/include/utils)
 endfunction(add_challenge)
 
 add_challenge(day1)
@@ -20,6 +19,7 @@ add_challenge(day7)
 add_challenge(day8)
 add_challenge(day9)
 add_challenge(day10)
+add_challenge(day11)
 
 add_custom_command(TARGET day1
     COMMAND ${CMAKE_COMMAND} -E create_symlink "${CMAKE_CURRENT_SOURCE_DIR}/data" "./data"

data

@@ -0,0 +1,20 @@
+#pragma once
+
+#include <stdint.h>
+#include <cmath>
+
+[[nodiscard]] constexpr size_t numOfDigits(uint64_t num) noexcept {
+    return static_cast<uint64_t>(std::log10(num) + 1);
+}
+
+[[nodiscard]] constexpr std::pair<uint64_t, uint64_t> splitNum(uint64_t num, size_t countOfDigits) noexcept {
+    // Calculate the power of 10 to split the number
+    const uint64_t splitPoint = countOfDigits / 2;
+    const uint64_t divisor = static_cast<uint64_t>(std::pow(10, splitPoint));
+
+    // Split the number
+    const uint64_t firstPart = num / divisor;
+    const uint64_t secondPart = num % divisor;
+
+    return {firstPart, secondPart};
+}

include/utils/numeric_algorithm.hpp

@@ -0,0 +1,90 @@
+#include "common_headers.hpp"
+#include "utils/numeric_algorithm.hpp"
+
+#include <cmath>
+#include <sstream>
+
+
+using HashTable = std::unordered_map<size_t, std::unordered_map<size_t, uint64_t>>;
+size_t calculateStones(size_t maxBlinks, size_t blinks, uint64_t num, HashTable& cache) { 
+
+    if(cache[num].count(blinks)) {
+        return cache[num][blinks];
+    }
+    if(blinks == maxBlinks) {
+        return 1;
+    }
+    if(num == 0) {
+        const auto stones = calculateStones(maxBlinks, blinks + 1, 1, cache);
+        cache[num][blinks] = stones ;
+    }
+    else if(auto countOfDigits = numOfDigits(num); countOfDigits % 2 == 0) {
+        const auto [num1, num2] = splitNum(num, countOfDigits);
+        
+        const auto stones1 = calculateStones(maxBlinks, blinks + 1, num1, cache);
+        const auto stones2 = calculateStones(maxBlinks, blinks + 1, num2, cache);
+        cache[num][blinks] = stones1 + stones2;
+    }
+    else {
+        const auto stones = calculateStones(maxBlinks, blinks + 1, num * 2024, cache);
+        cache[num][blinks] = stones;
+    }
+
+    return cache[num][blinks];
+}
+
+size_t solveFirstPart(const std::vector<uint64_t>& stones, size_t maxBlinks) { 
+    HashTable cache;
+    size_t stoneCounter{};
+    for(auto it = stones.rbegin(); it != stones.rend(); ++it) {
+        stoneCounter += calculateStones(maxBlinks, 0, *it, cache);
+    }
+    return stoneCounter;
+}
+
+std::vector<uint64_t> lineParser(const std::string& line) {
+    std::stringstream ss(line);
+    uint64_t num{};
+    std::vector<uint64_t> nums;
+    while ((ss >> num))
+    {
+        nums.push_back(num);
+    }
+    return nums;
+}
+
+void printHelp()
+{
+    std::cerr << "\nUsage:\n"
+    << "The program requires 2 args: (part1, part2) and the path to the file."
+    << "\nFor example, ./day7 part1 data/day7.txt";
+}
+
+int main(int argc, char* argv[])
+{
+    if(argc != 3) {
+        printHelp();
+        return 1;
+    }
+
+    std::string_view task{argv[1]};
+    if(task != "part1" && task != "part2") {
+        std::cerr << "\nfirst arg can be either `part1` or `part2`\n";
+        printHelp();
+        return 1;
+    }
+    
+    std::vector<std::vector<uint64_t>> inputVec;
+    readInput(argv[2], std::back_inserter(inputVec), lineParser);
+
+    if(task == "part1") {
+        const size_t maxBlinks{25};
+        std::cout << solveFirstPart(inputVec.at(0), maxBlinks);
+    }
+    else {
+        const size_t maxBlinks{75};
+        std::cout << solveFirstPart(inputVec.at(0), maxBlinks);
+    }
+
+    return 0;
+}

src/day11.cpp

@@ -1,4 +1,6 @@
 #include "common_headers.hpp"
+#include "utils/numeric_algorithm.hpp"
+
 #include <sstream>
 #include <limits>
 #include <cmath>
@@ -11,7 +13,7 @@ struct Equation final
 };
 
 [[nodiscard]] constexpr int64_t cat(int64_t a, int64_t b) noexcept {
-    const int multiplier = std::pow(10, static_cast<int>(std::log10(b) + 1));
+    const int multiplier = std::pow(10, numOfDigits(b));
     return a * multiplier + b;
 };