doc: NEWS: say quadratic and linear, rather than O(N^2) and O(N)

* NEWS: Use a slightly less technical description.
Suggested by Andreas Schwab.

diff --git a/NEWS b/NEWS
index ec41ca77329fb544013c221e18c6bf46ce19c916..980fb543fdc8f161976febbc0b5e21e92f329c49 100644 (file)
--- a/NEWS
+++ b/NEWS
@@ -13,12 +13,13 @@ GNU coreutils NEWS                                    -*- outline -*-
   This makes rm -rf significantly faster (400-500%) in some pathological
   cases, and slightly slower (20%) in at least one pathological case.
 
-  rm -r deletes deep hierarchies more efficiently.  Before, it took O(N^2)
-  time, now it takes O(N), where N is the depth of the hierarchy.  However,
-  this improvement is not as pronounced as might be expected for very
-  deep trees, because prior to this change, for any relative name length
-  longer than 8KiB, rm -r would sacrifice official conformance to avoid the
-  disproportionate O(N^2) performance penalty.  Leading to another improvement:
+  rm -r deletes deep hierarchies more efficiently.  Before, execution time
+  was quadratic in the depth of the hierarchy, now it is merely linear.
+  However, this improvement is not as pronounced as might be expected for
+  very deep trees, because prior to this change, for any relative name
+  length longer than 8KiB, rm -r would sacrifice official conformance to
+  avoid the disproportionate quadratic performance penalty.  Leading to
+  another improvement:
 
   rm -r is now slightly more standards-conformant when operating on
   write-protected files with relative names longer than 8KiB.