All possible strings of any length that can be formed from a given string

Given a string of distinct characters, print all possible strings of any length that can be formed from given string characters. Examples:

Input: abc
Output: a b c abc ab ac bc bac bca 
 cb ca ba cab cba acb
Input: abcd
Output: a b ab ba c ac ca bc cb abc acb bac
 bca cab cba d ad da bd db abd adb bad 
 bda dab dba cd dc acd adc cad cda dac 
 dca bcd bdc cbd cdb dbc dcb abcd abdc 
 acbd acdb adbc adcb bacd badc bcad bcda 
 bdac bdca cabd cadb cbad cbda cdab cdba 
 dabc dacb dbac dbca dcab dcba 

Approach 1:

The generation of all strings include the following steps. 

1) Generate all subsequences of given string. 

2) For every subsequence 'subs', print all permutations of 'subs' 
Below is C++ implementation. It uses next_permutation function in C++. 

a b ab ba c ac ca bc cb abc acb bac bca cab cba 

Time complexity: O(n * 2^n * n!)
Auxiliary Space : O(2^n * n)

Approach 2 :

• Generate all possible combinations of the given string using a bitmask.
• For each combination, generate all possible permutations of the characters in that combination.
• Print each permutation.

Below is the code for the above approach:

a b ab ba c ac ca bc cb abc acb bac bca cab cba 

Time complexity : O(n * 2^n * n!)

Auxiliary Space : O(n)