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Lexicographically smallest string which is not a subsequence of given string | Function to find lexicographically smallest string that is not a subsequence of S.
Variable to store frequency of a.
Calculate frequency of a.
Initialize string consisting of freq number of a.
Change the last digit to b.
Add another ' a ' to the string.
Return tha answer string.
Driver code.
Input.
Function call"
Solution in Python:

Write me a code to lexicographically smallest string which is not a subsequence of given string and the other steps required?
assistant
#Here is code to lexicographically smallest string which is not a subsequence of given string and the other steps required.
 def smallestNonSubsequence ( S , N ) :
	freq = 0
	for i in range ( N ) :
		if ( S [ i ] == ' a ' ) :
			freq += 1
	ans = " "
	for i in range ( freq ) :
		ans += ' a '
	if ( freq == N ) :
		ans = ans . replace ( ans [ freq - 1 ] , ' b ' )
	else :
		ans += ' a '
	return ans
if __name__ == ' _ _ main _ _ ' :
	S = " abcdefghijklmnopqrstuvwxyz "
	N = len ( S )
	print ( smallestNonSubsequence ( S , N ) )