feat: day1_1

2024/Day1/src/main.c

@@ -1,5 +1,84 @@
 #include <stdio.h>
-int main(void) {
+#include <stdlib.h>
-	printf("TEST");
+#include <string.h>
-	return 0;
+
+#define BUFFER_SIZE 256
+
+int count_lines(char *filename);
+int compare_ints(const void *a, const void *b);
+
+int main() {
+  FILE *file;
+  char filename[] = "input.txt";
+  char *buffer = malloc(BUFFER_SIZE);
+  char *saveptr;
+  char *current_number_string;
+  const int lines = count_lines(filename);
+  int *first_numbers = malloc(lines * sizeof(int));
+  int *second_numbers = malloc(lines * sizeof(int));
+  int current_position = 0;
+  int sum = 0;
+
+  file = fopen(filename, "r");
+
+  if (file == NULL) {
+    perror("Error opening file");
+    return 1;
+  }
+
+  while (fgets(buffer, BUFFER_SIZE, file) != NULL) {
+    char *line = buffer;
+    int is_first = 1;
+    while ((current_number_string = strtok_r(line, "   ", &saveptr))) {
+      if (current_number_string[strlen(current_number_string) - 1] == '\n') {
+        current_number_string[strlen(current_number_string) - 1] = '\0';
+      }
+      if (is_first) {
+	first_numbers[current_position] = atoi(current_number_string);
+      } else {
+	second_numbers[current_position] = atoi(current_number_string);
+      }
+      is_first ^= 1;
+      if (line) {
+        line = NULL;
+      }
+    }
+    current_position++;
+  }
+  qsort(first_numbers, lines, sizeof(int), compare_ints);
+  qsort(second_numbers, lines, sizeof(int), compare_ints);
+  
+  for (int i = 0; i < lines; i++) {
+	int difference = abs(first_numbers[i] - second_numbers[i]);
+	sum += difference;
+  }
+
+  printf("%d\n", sum);
+  fclose(file);
+
+  return 0;
+}
+
+int count_lines(char *filename) {
+  char c;
+  int lines = 0;
+  FILE *file = fopen(filename, "r");
+
+  if (!file) {
+    return 0;
+  }
+
+  while (!feof(file)) {
+    c = fgetc(file);
+    if (c == '\n') {
+      lines++;
+    }
+  }
+
+  fclose(file);
+  return lines;
+}
+
+int compare_ints(const void *a, const void *b) {
+    return (*(int *)a - *(int *)b);
 }