# Python Program to Join Equi-hierarchy Strings

• Last Updated : 05 Apr, 2021

Given a list of strings with several hierarchies, the task is to write a python program to join those which have the same hierarchies.

Elements in the same dimension before a dimension change are known to be in the same hierarchy.

Input : test_list = [“gfg “, ” best “, [” for “, ” all “], ” all “, [” CS ” , ” geeks “]]

Output : [‘gfg  best ‘, [‘ for  all ‘], ‘ all ‘, [‘ CS  geeks ‘]]

Explanation : Strings at similar hierarchy as joined.

Input : test_list = [“gfg “, ” best “, [” for “, ” all “], [” CS ” , ” geeks “]]

Output : [‘gfg  best ‘, [‘ for  all ‘], [‘ CS  geeks ‘]]

Explanation : Strings at similar hierarchy as joined.

Method 1 : Using type(), loop, recursion and join()

In this, the list element is checked to be string using type(), if found, the joining task is performed using join for that hierarchy. If element is found to be list, the inner list is recurred for similar logic for next level of hierarchy.

Example:

## Python3

 def hierjoin(test_list):     res = []     temp = []     val = None     for sub in test_list:            # if string then appended         if type(sub) == str:             temp.append(sub)            # if list, the string is joined for hierarchy         # recurred for inner list         else:             res.append(''.join(temp))             temp = []             val = hierjoin(sub)             res.append(val)     if temp != []:         res.append(''.join(temp))     return res       # initializing list test_list = ["gfg ", " best ", [" for ", " all "],              " all ", [" CS ", " geeks "]]    # printing original list print("The original list is : " + str(test_list))    # calling recursion res = hierjoin(test_list)    # printing result print("The joined strings : " + str(res))

Output:

The original list is : [‘gfg ‘, ‘ best ‘, [‘ for ‘, ‘ all ‘], ‘ all ‘, [‘ CS ‘, ‘ geeks ‘]]

The joined strings : [‘gfg  best ‘, [‘ for  all ‘], ‘ all ‘, [‘ CS  geeks ‘]]

Method 2 : Using join(), map(), recursion and groupby()

In this equihierarchy groups are formed using groupby(). Then map() is used to call the recursion function for inner hierarchy of list strings.

Example:

## Python3

 from itertools import groupby       def hierjoin(test_list):        # groups are formed for similar hierarchy using groupby     return [idx for x, y in groupby(test_list, key=str.__instancecheck__)             for idx in ([''.join(y)] if x else map(hierjoin, y))]       # initializing list test_list = ["gfg ", " best ", [" for ", " all "],              " all ", [" CS ", " geeks "]]    # printing original list print("The original list is : " + str(test_list))    # calling recursion res = hierjoin(test_list)    # printing result print("The joined strings : " + str(res))

Output:

The original list is : [‘gfg ‘, ‘ best ‘, [‘ for ‘, ‘ all ‘], ‘ all ‘, [‘ CS ‘, ‘ geeks ‘]]

The joined strings : [‘gfg  best ‘, [‘ for  all ‘], ‘ all ‘, [‘ CS  geeks ‘]]

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