Added a shorter solution for the directory diff exercise (bregman-arie#344)

Signed-off-by: Fabio Kruger <10956489+krufab@users.noreply.github.com>

Author: krufab

topics/shell/README.md

@@ -14,7 +14,7 @@
 |Sum|Functions|[Exercise](sum.md)|[Solution](solutions/sum.md) | Basic
 |Number of Arguments|Case Statement|[Exercise](num_of_args.md)|[Solution](solutions/num_of_args.md) | Basic
 |Empty Files|Misc|[Exercise](empty_files.md)|[Solution](solutions/empty_files.md) | Basic
-|Directories Comparison|Misc|[Exercise](directories_comparison.md)| :( | Basic
+|Directories Comparison|Misc|[Exercise](directories_comparison.md)|[Solution](solutions/directories_comparison.md) | Basic
 |It's alive!|Misc|[Exercise](host_status.md)|[Solution](solutions/host_status.md) | Intermediate
 
 ## Shell Scripting - Self Assessment

topics/shell/solutions/directories_comparison.md

@@ -4,7 +4,7 @@
 
 1. You are given two directories as arguments and the output should be any difference between the two directories
 
-### Solution
+### Solution 1
 
 Suppose the name of the bash script is ```dirdiff.sh```
 
@@ -26,5 +26,12 @@ then
 fi
 
 diff -q $1 $2
+```
+
+### Solution 2
 
-```
+With gnu find, you can use diff to compare directories recursively.
+
+```shell
+diff --recursive directory1 directory2
+```