human
Write me a code to minimum number of subsequences required to convert one string to another using Greedy Algorithm and the other steps required given the following:
Minimum number of subsequences required to convert one string to another using Greedy Algorithm | Function to find the minimum number of subsequences required to convert one to another S2 == A and S1 == B.
At least 1 subsequence is required Even in best case , when A is same as B.
size of B.
size of A.
Create an 2D array next [ ] [ ] of size 26 * sizeOfB to store the next occurrence of a character ( ' a ' to ' z ' ) as an index [ 0 , sizeOfA - 1 ].
Loop to Store the values of index.
If the value of next [ i ] [ j ] is infinite then update it with next [ i ] [ j + 1 ].
Greedy algorithm to obtain the maximum possible subsequence of B to cover the remaining of A using next subsequence.
Loop to iterate over the A.
Condition to check if the character is not present in the B.
Condition to check if there is an element in B matching with character A [ i ] on or next to B [ pos ] given by next [ A [ i ] - ' a ' ] [ pos ].
Condition to check if reached at the end of B or no such element exists on or next to A [ pos ] , thus increment number by one and reinitialise pos to zero.
Driver Code"
How can the above be solved in Python?
assistant
#Here is code to minimum number of subsequences required to convert one string to another using Greedy Algorithm and the other steps required.
 def findMinimumSubsequences ( A , B ) :
	numberOfSubsequences = 1
	sizeOfB = len ( B )
	sizeOfA = len ( A )
	inf = 1000000
	next = [ [ inf for i in range ( sizeOfB ) ] for i in range ( 26 ) ]
	for i in range ( sizeOfB ) :
		next [ ord ( B [ i ] ) - ord ( ' a ' ) ] [ i ] = i
	for i in range ( 26 ) :
		for j in range ( sizeOfB - 2 , - 1 , - 1 ) :
			if ( next [ i ] [ j ] == inf ) :
				next [ i ] [ j ] = next [ i ] [ j + 1 ]
	pos = 0
	i = 0
	while ( i < sizeOfA ) :
		if ( pos == 0 and next [ ord ( A [ i ] ) - ord ( ' a ' ) ] [ pos ] == inf ) :
			numberOfSubsequences = - 1
			break
		elif ( pos < sizeOfB and next [ ord ( A [ i ] ) - ord ( ' a ' ) ] [ pos ] < inf ) :
			nextIndex = next [ ord ( A [ i ] ) - ord ( ' a ' ) ] [ pos ] + 1
			pos = nextIndex
			i += 1
		else :
			numberOfSubsequences += 1
			pos = 0
	return numberOfSubsequences
if __name__ == ' _ _ main _ _ ' :
	A = " aacbe "
	B = " aceab "
	print ( findMinimumSubsequences ( A , B ) )