17

17/CMakeLists.txt

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+cmake_minimum_required(VERSION 3.10)
+set(CMAKE_CXX_STANDARD 14)
+set(CMAKE_CXX_STANDARD_REQUIRED True)
+set(CMAKE_EXPORT_COMPILE_COMMANDS ON)
+enable_language(CXX)
+
+project(AoC17)
+
+if(APPLE)
+    include_directories(/usr/local/include)
+    link_directories(/usr/local/lib)
+endif()
+
+if(WIN32)
+	add_executable(${CMAKE_PROJECT_NAME} WIN32)
+else()
+	add_executable(${CMAKE_PROJECT_NAME})
+endif()
+
+target_sources(${CMAKE_PROJECT_NAME}
+	PRIVATE main.cpp
+	)

17/input

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+target area: x=209..238, y=-86..-59

17/main.cpp

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+#include <algorithm>
+#include <deque>
+#include <fstream>
+#include <iostream>
+#include <sstream>
+#include <unordered_map>
+#include <unordered_set>
+#include <vector>
+
+using Area = std::pair<std::pair<long, long>, std::pair<long, long>>;
+
+Area getTargetArea(const std::string &file_name) {
+    Area area{};
+
+    std::ifstream file(file_name);
+    std::string str;
+    std::getline(file, str);
+    std::stringstream ss(str);
+
+    std::string tmp;
+    char tmp_char;
+    long x1, x2, y1, y2;
+    ss >> tmp;
+    ss >> tmp;
+    ss >> tmp_char;
+    ss >> tmp_char;
+
+    ss >> x1;
+    ss >> tmp_char;
+    ss >> tmp_char;
+    ss >> x2;
+    ss >> tmp_char;
+    ss >> tmp_char;
+    ss >> tmp_char;
+    ss >> y1;
+    ss >> tmp_char;
+    ss >> tmp_char;
+    ss >> y2;
+    if (x1 < x2) {
+        area.first = { x1, x2 };
+    } else {
+        area.first = { x2, x1 };
+    }
+    if (y1 < y2) {
+        area.second = { y1, y2 };
+    } else {
+        area.second = { y2, y1 };
+    }
+
+    return area;
+}
+
+uint64_t sumUntilN(uint64_t n) {
+    return (n * (n + 1)) / 2;
+}
+
+long getMaxYSpeed(long lowest_area_y) {
+    return abs(lowest_area_y) - 1;
+}
+
+uint64_t part1(const Area &area) {
+    return sumUntilN(getMaxYSpeed(area.second.first));
+}
+
+bool willEverReach(long min_x, long max_x, long min_y, long max_y,
+                   long initial_x, long initial_y) {
+    std::pair<long, long> pos = { 0, 0 };
+    while (true) {
+        pos.first += initial_x;
+        pos.second += initial_y;
+        if (pos.first >= min_x && pos.first <= max_x && pos.second <= min_y &&
+            pos.second >= max_y) {
+            return true;
+        }
+        if (initial_x == 0 && pos.first < min_x) {
+            break;
+        }
+        if (pos.first > max_x) {
+            break;
+        }
+        if (pos.second < max_y) {
+            break;
+        }
+        if (initial_x > 0) {
+            initial_x--;
+        }
+        initial_y--;
+    }
+    return false;
+}
+
+uint64_t part2(Area &area) {
+    uint64_t valid_trajectory = 0;
+    auto max_dist_y = abs(area.second.first);
+    auto max_dist_x = area.first.second;
+
+    for (long y = getMaxYSpeed(area.second.first); y >= area.second.first;
+         y--) {
+        for (long x = 0; x <= area.first.second; x++) {
+            if (willEverReach(area.first.first, area.first.second,
+                              area.second.second, area.second.first, x, y)) {
+                valid_trajectory++;
+            }
+        }
+    }
+
+    return valid_trajectory;
+}
+
+int main(int argc, char **argv) {
+    if (argc < 2) {
+        std::cerr << "You must provide input file!" << std::endl;
+        return 1;
+    }
+    auto area = getTargetArea(argv[1]);
+    std::cout << "The highest possible y is \033[91;1m" << part1(area)
+              << "\033[0m." << std::endl;
+    std::cout << "There are \033[91;1m" << part2(area)
+              << "\033[0m possible trajectories." << std::endl;
+    return 0;
+}