Solution/007

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

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+'''
+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.   
+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]`. 
+
+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. 
+
+Create a main program that displays a run-length encoded list and the result of decoding it.
+'''
+
+def decompression(array):
+    if len(array) == 0:
+        return []
+
+    value = array[0]
+    count = array[1]
+    finalvalue = [value] * count + decompression(array[2:])
+
+    return finalvalue
+
+def main():
+    array = ["A", 12, "B", 4, "A", 6, "B", 1]
+    print(decompression(array))
+
+if __name__ == "__main__":
+    main()

projects/007-run-length-encoding/python/main.py

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+'''
+Write a recursive function that implements the run-length compression technique described in Run-Lenght Decoding Exercise. 
+
+Your function will take a list or a string as its only argu- ment. It should return the run-length compressed list as its only result. 
+
+Include a main program that reads a string from the user, compresses it, and displays the run-length
+encoded result.
+
+Hint: You may want to include a loop inside the body of your recursive function.
+'''
+
+def compression(array):
+    if len(array) == 0:
+        return []
+
+    value = array[0]
+    count = 1
+
+    while count < len(array) and array[count] == value:
+        count += 1
+
+    return [value, count] + compression(array[count:])
+
+def main():
+    array = ["A", "A", "A", "A", "A", "A", "A", "A", "A", "A", "A", "A", "B", "B", "B", "B", "A", "A", "A", "A", "A", "A", "B"]
+    compressed = compression(array)
+    print(compressed)
+
+if __name__ == "__main__":
+    main()