# 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' => ''

def get_noduplicate(str)
    str_orig = str.dup

    while str =~ /(\w)\1/
        str.gsub!(/(\w)\1/, '')
    end

    printf "'%s' -> '%s'\n", str_orig, str;
end

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)