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# Task 1: Duplicate Removals
# Submitted by: Mohammad Sajid Anwar
#
# You are given a string, $str, consisting of lowercase English letters.
#
# Write a script to return the final string after all duplicate removals have been made. Repeat duplicate removals on the given string until we no longer can.
#
# A duplicate removal consists of choosing two adjacent and equal letters and removing them.
#
# Example 1
# Input: $str = 'abbaca'
# Output: 'ca'
#
# Step 1: Remove 'bb' => 'aaca'
# Step 2: Remove 'aa' => 'ca'
#
# Example 2
# Input: $str = 'azxxzy'
# Output: 'ay'
#
# Step 1: Remove 'xx' => 'azzy'
# Step 2: Remove 'zz' => 'ay'
#
# Example 3
# Input: $str = 'aaaaaaaa'
# Output: ''
#
# Step 1: Remove 'aa' => 'aaaaaa'
# Step 2: Remove 'aa' => 'aaaa'
# Step 3: Remove 'aa' => 'aa'
# Step 4: Remove 'aa' => ''
#
# Example 4
# Input: $str = 'aabccba'
# Output: 'a'
#
# Step 1: Remove 'aa' => 'bccba'
# Step 2: Remove 'cc' => 'bba'
# Step 3: Remove 'bb' => 'a'
#
# Example 5
# Input: $str = 'abcddcba'
# Output: ''
#
# Step 1: Remove 'dd' => 'abccba'
# Step 2: Remove 'cc' => 'abba'
# Step 3: Remove 'bb' => 'aa'
# Step 4: Remove 'aa' => ''
import re
def get_noduplicate(str):
str_orig = str
while re.search(r'([a-z])\1', str):
str = re.sub(r'([a-z])\1', r'', str)
print("'%s' -> '%s'" % ( str_orig, str ) )
if __name__ == "__main__":
str = 'abbaca'
get_noduplicate(str)
str = 'azxxzy'
get_noduplicate(str)
str = 'aaaaaaaa'
get_noduplicate(str)
str = 'aabccba'
get_noduplicate(str)
str = 'abcddcba'
get_noduplicate(str)
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