Committing days 1-4

01/01.c

@@ -0,0 +1,57 @@
+#include <stdio.h>
+#include <stdlib.h>
+#include <stdint.h>
+
+int main(int argc, char **argv) {
+
+    // Get filename as an argument, defaults to "input.txt"
+    char *path = (argc > 1) ? argv[1] : "input.txt";
+
+    if (!path)
+    {
+        printf("Requires input file.\n");
+        return 1;
+    }
+
+    FILE *file = fopen(path, "r");
+
+    if (!file)
+    {
+        printf("Could not find file.");
+        return 1;
+    }
+
+    int8_t firstdigit = -1;
+    int8_t lastdigit = -1;
+    uint32_t sum = 0;
+    char current = 0;
+
+    while (current != EOF)
+    {
+        current = fgetc(file);
+
+        if (current == '\n')
+        {
+            if (lastdigit == -1) lastdigit = firstdigit;
+            sum += (firstdigit * 10) + lastdigit;
+            firstdigit = -1;
+            lastdigit = -1;
+            continue;
+        }
+
+        if (current < '0' || current > '9') continue;
+
+        if (firstdigit == -1)
+        {
+            firstdigit = current - '0';
+        }
+        else
+        {
+            lastdigit = current - '0';
+        }
+    }
+
+    printf("Sum: %d\n", sum);
+
+    return 0;
+}