9.17

--- mm.c	2021-02-25 07:26:33.315926002 +0000
+++ mm.9.17.c	2021-02-25 07:26:33.315926002 +0000
@@ -41,6 +41,7 @@
 
 /* Global variables */
 static char *heap_listp = 0;  /* Pointer to first block */
+static char *rover;           /* Next fit rover */
 
 /* Function prototypes for internal helper routines */
 static void *extend_heap(size_t words);
@@ -69,6 +70,7 @@
   heap_listp += (2*WSIZE);                     //line:vm:mm:endinit
   /* $end mminit */
 
+  rover = heap_listp;
   /* $begin mminit */
 
   /* Extend the empty heap with a free block of CHUNKSIZE bytes */
@@ -177,6 +179,10 @@
     bp = PREV_BLKP(bp);
   }
   /* $end mmfree */
+  /* Make sure the rover isn't pointing into the free block */
+  /* that we just coalesced */
+  if ((rover > (char *)bp) && (rover < NEXT_BLKP(bp)))
+    rover = bp;
   /* $begin mmfree */
   return bp;
 }
@@ -290,16 +296,20 @@
 {
   /* $end mmfirstfit */
 
-  /* $begin mmfirstfit */
-  /* First-fit search */
-  void *bp;
-
-  for (bp = heap_listp; GET_SIZE(HDRP(bp)) > 0; bp = NEXT_BLKP(bp)) {
-    if (!GET_ALLOC(HDRP(bp)) && (asize <= GET_SIZE(HDRP(bp)))) {
-      return bp;
-    }
-  }
-  return NULL; /* No fit */
+  /* Next fit search */
+  char *oldrover = rover;
+
+  /* Search from the rover to the end of list */
+  for ( ; GET_SIZE(HDRP(rover)) > 0; rover = NEXT_BLKP(rover))
+    if (!GET_ALLOC(HDRP(rover)) && (asize <= GET_SIZE(HDRP(rover))))
+      return rover;
+
+  /* search from start of list to old rover */
+  for (rover = heap_listp; rover < oldrover; rover = NEXT_BLKP(rover))
+    if (!GET_ALLOC(HDRP(rover)) && (asize <= GET_SIZE(HDRP(rover))))
+      return rover;
+
+  return NULL;  /* no fit found */
 }
 /* $end mmfirstfit */