Day4

day4/c/day4.c

@@ -0,0 +1,94 @@
+#include <stdio.h>
+#include <stdlib.h>
+#include <omp.h>
+
+#define MAX_DIMENSION 512
+
+// Row, Column
+const int directions[][2] = {
+    {0,1}, // Right
+    {0,-1}, // Left
+    {1,0}, // Down
+    {-1,0}, // Up
+    {1,1}, // Right-Down
+    {1,-1}, // Left-Down
+    {-1,-1}, // Left-Up
+    {-1,1}, // Right-Up
+};
+
+const char sequence[] = {'X', 'M', 'A', 'S'};
+
+#define directions_len sizeof(directions) / sizeof(directions[0])
+#define sequence_len sizeof(sequence) / sizeof(sequence[0])
+
+int main() {
+    char *p, c;
+
+    int rows = 0, columns = 0;
+    char **characters = calloc(MAX_DIMENSION, sizeof(characters[0]));
+    characters[rows] = calloc(MAX_DIMENSION, sizeof(characters[0][0]));
+    p = characters[rows];
+
+    while ((c = getchar()) != EOF) {
+        *p++ = c;
+        if (c != '\n') {
+            if (rows == 0) {
+                columns++;
+            }
+            continue;
+        }
+
+        rows++;
+        characters[rows] = calloc(MAX_DIMENSION, sizeof(characters[0][0]));
+        p = characters[rows];
+    }
+
+    int count = 0;
+    int count2 = 0;
+#pragma omp parallel for
+    for (int i = 0; i < rows; i++) {
+        for (int j = 0; j < columns; j++) {
+            for (int k = 0; k < directions_len; k++) {
+                int found = 1;
+                for (int l = 0; l < sequence_len; l++) {
+                    int row = i + l * directions[k][0];
+                    int column = j + l * directions[k][1];
+                    if (row < 0 || column < 0 || row > rows - 1 || column > columns - 1) {
+                        found = 0;
+                        break;
+                    }
+
+                    if (sequence[l] != characters[row][column]) {
+                        found = 0;
+                        break;
+                    }
+                }
+                if (found)
+#pragma omp critical
+                {
+                    count++;
+                }
+            }
+
+            // Part2
+            if (characters[i][j] == 'A' && i > 0 && i < rows - 1 && j > 0 && j < columns - 1) {
+                if (
+                        ((characters[i-1][j-1] == 'M' && characters[i+1][j+1] == 'S') || (characters[i-1][j-1] == 'S' && characters[i+1][j+1] == 'M')) &&
+                        ((characters[i+1][j-1] == 'M' && characters[i-1][j+1] == 'S') || (characters[i+1][j-1] == 'S' && characters[i-1][j+1] == 'M'))
+                    )
+#pragma omp critical
+                {
+                    count2++;
+                }
+            }
+        }
+    }
+
+    for (int i = 0; i < rows; i++) {
+        free(characters[i]);
+    }
+    free(characters);
+
+    printf("%i\n", count);
+    printf("%i\n", count2);
+}