Index: aoc2024.c
==================================================================
--- aoc2024.c
+++ aoc2024.c
@@ -33,20 +33,24 @@
                 if (ndisk == rdisk) {
                     // assume it works
                     rdisk = (13*rdisk)/8;
                     disk = realloc(disk, rdisk * sizeof *disk);
                 }
-                disk[ndisk++] = -1;
+                disk[ndisk++] = -1 * (*data - '0');
             }
             data++;
         }
     }
+    // copy disk
+    int *diskcopy = malloc(ndisk * sizeof *disk);
+    memcpy(diskcopy, disk, ndisk * sizeof *disk);
+
     int *left = disk, *right = disk + ndisk;
     for (;;) {
-        while (*left != -1) left++;
+        while (*left >= 0) left++;
         if (left >= right) break;
-        while (right[-1] == -1) right--;
+        while (right[-1] < 0) right--;
         // swap *left and right[-1]
         int tmp = *--right;
         *right = *left;
         *left++ = tmp;
     }
@@ -56,10 +60,13 @@
         chksum += (size_t)disk[index] * index;
         index++;
     }
     printf("%llu\n", chksum);
     free(disk);
+
+    // part 2
+    free(diskcopy);
 }
 
 /* === aoc202408 =======================================================
    Oh! another square of text!
    Idea: for all points p with an antenna find all points q>p with