solution/m3-006

projects/006-run-length-decoding/README.md

@@ -1,22 +1,22 @@
 # Run-Length Decoding
 
-Run-length encoding is a simple data compression technique that can be effective 
-when repeated values occur at adjacent positions within a list. 
+Run-length encoding is a simple data compression technique that can be effective
+when repeated values occur at adjacent positions within a list.
 
-Compression is achieved by replacing groups of repeated values with one copy of the value, 
-followed by the number of times that it should be repeated.   
+Compression is achieved by replacing groups of repeated values with one copy of the value,
+followed by the number of times that it should be repeated.  
 For example, the list  
 `["A", "A", "A", "A", "A", "A", "A", "A", "A", "A", "A", "A", "B", "B", "B","B","A","A","A","A","A","A","B"]`  
-would be compressed as `["A",12,"B",4,"A",6,"B",1]`. 
+would be compressed as `["A",12,"B",4,"A",6,"B",1]`.
 
 Decompression is performed by replicating each value in the list the number of times indicated.
 
-Write a recursive function that decompresses a run-length encoded list. 
-Your recursive function will take a run-length compressed list as its only argument. 
-It will return the decompressed list as its only result. 
+Write a recursive function that decompresses a run-length encoded list.
+Your recursive function will take a run-length compressed list as its only argument.
+It will return the decompressed list as its only result.
 
 Create a main program that displays a run-length encoded list and the result of decoding it.
-		 
+
 # Documentation
 
 For this project solution you may use:

projects/006-run-length-decoding/python/main.py

@@ -0,0 +1,37 @@
+def decode_compressed_list(comp_ls):
+    if len(comp_ls)>0:
+        elem=comp_ls[0]
+        comp_ls.remove(comp_ls[0])
+        num=comp_ls[0]
+        comp_ls.remove(comp_ls[0])
+        return [elem]*num+decode_compressed_list(comp_ls)
+    else:
+        return []
+
+def main():
+    StructureIsWrong=True
+    while StructureIsWrong:
+        SyntaxIsWrong=True
+        while SyntaxIsWrong:
+            try:
+                comp_ls=eval(input('Please, enter a string of this type [string,integer,string,integer...]: '))
+                SyntaxIsWrong=False
+            except SyntaxError:
+                print("Wrong list syntax, retry!")
+
+        StructureIsWrong=False
+        if len(comp_ls)%2>0:
+            StructureIsWrong=True
+        else:
+            strings=comp_ls[0:2:]
+            ints=comp_ls[1:2:]
+            for i,j in zip(strings,ints):
+                if not (type(i)==str and type(j)==int):
+                    StructureIsWrong=True
+
+    ls=comp_ls.copy()
+    decomp_list=decode_compressed_list(ls)
+    print('Compressed list: {}\n\nDecompressed list: {}'.format(comp_ls,decomp_list))
+
+if __name__=='__main__':
+    main()