Day 4

d4/main.cxx

@@ -1,15 +1,122 @@
 #include <iostream>
-#include <fstream>
+#include <sstream>
+#include <vector>
 
 using std::cout, std::endl;
 
-int main() {
+constexpr const char content[] = {
-    std::ifstream file{"../d4/input.txt"};
+    #embed "input.txt"
-    std::string line;
+};
 
-    while (std::getline(file, line)) {
+int count_xmas(const std::vector<std::string> &grid, int i, int j) {
-        
+
+    bool up{true}, down{true}, left{true}, right{true}, up_left{true}, up_right{true}, down_left{true}, down_right{true};
+    for(auto d : {std::pair{1, 'M'}, std::pair{2, 'A'}, std::pair{3, 'S'}}) {
+        if(up && (i - d.first < 0 || grid[i - d.first][j] != d.second)) {
+            up = false;
+        } 
+
+        if(down && (i + d.first >= grid[i].size() || grid[i + d.first][j] != d.second)) {
+            down = false;
+        }
+
+        if(right && (j + d.first >= grid[i].size() || grid[i][j + d.first] != d.second)) {
+            right = false;
+        }
+
+        if(left && (j - d.first < 0 || grid[i][j - d.first] != d.second)) {
+            left = false;
+        }
+
+        if(up_right && (i - d.first < 0 || j + d.first >= grid[i].size() || grid[i - d.first][j + d.first] != d.second)) {
+            up_right = false;
+        }
+
+        if(up_left && (i - d.first < 0 || j - d.first < 0 || grid[i - d.first][j - d.first] != d.second)) {
+            up_left = false;
+        }
+
+        if(down_right && (i + d.first >= grid[i].size() || j + d.first >= grid[i].size() || grid[i + d.first][j + d.first] != d.second)) {
+            down_right = false;
+        }
+
+        if(down_left && (i + d.first >= grid[i].size() || j - d.first < 0 || grid[i + d.first][j - d.first] != d.second)) {
+            down_left = false;
+        }
+    } 
+    
+    return up + down + left + right + up_left + up_right + down_left + down_right;    
+}
+
+void part_1() {
+    std::istringstream input_stream(content);
+    std::string line;
+    std::vector<std::string> grid;
+
+    while (std::getline(input_stream, line)) {
+        grid.push_back(line);
+    }
+
+    int count_acc{0};
+    for(int i = 0; i < grid.size(); i++) {
+        for(int j = 0; j < grid[i].size(); j++) {
+            if(grid[i][j] == 'X') {
+               count_acc += count_xmas(grid, i, j); 
+            } 
+        }
+    }
+
+    cout << count_acc << endl;
+}
+
+
+bool is_mas_cross(const std::vector<std::string>& grid, int i, int j) {
+    char up_right_letter, up_left_letter, down_right_letter, down_left_letter;
+    if(i - 1 >= 0 && j + 1 < grid[i].size() && (grid[i - 1][j + 1] == 'M' || grid[i - 1][j + 1] == 'S')) {
+        up_right_letter = grid[i - 1][j + 1];
+        down_left_letter = up_right_letter == 'M' ? 'S' : 'M';
+    } else {
+        return false;
+    }
+    if(i - 1 >= 0 && j - 1 >= 0 && (grid[i - 1][j - 1] == 'M' || grid[i - 1][j - 1] == 'S')) {
+        up_left_letter = grid[i - 1][j - 1];
+        down_right_letter = up_left_letter == 'M' ? 'S' : 'M';
+    } else {
+        return false;
+    }
+    if(i + 1 >= grid[i].size() || j + 1 >= grid[i].size() || grid[i + 1][j + 1] != down_right_letter) {
+        return false;
+    }
+    if(i + 1 >= grid[i].size() || j - 1 < 0 || grid[i + 1][j - 1] != down_left_letter) { 
+        return false;
     }
     
+    return true;
+}
+
+void part_2() {
+    std::istringstream input_stream(content);
+    std::string line;
+    std::vector<std::string> grid;
+
+    while (std::getline(input_stream, line)) {
+        grid.push_back(line);
+    }
+
+    int count_acc{0};
+    for(int i = 0; i < grid.size(); i++) {
+        for(int j = 0; j < grid[i].size(); j++) {
+            if(grid[i][j] == 'A') {
+               count_acc += is_mas_cross(grid, i, j);
+            } 
+        }
+    }
+
+    cout << count_acc << endl;
+} 
+
+int main() {
+    part_1();
+    part_2();
     return 0;
 }