human
Transform string str1 into str2 by taking characters from string str3 | Function to check whether str1 can be transformed to str2.
To store the frequency of characters of string str3.
Declare two pointers & flag.
Traverse both the string and check whether it can be transformed.
If both pointers point to same characters increment them.
If the letters don 't match check  if we can find it in string C.
If the letter is available in string str3 , decrement it 's  frequency & increment the ptr2.
If letter isn 't present in str3[]  set the flag to false and break.
If the flag is true and both pointers points to their end of respective strings then it is possible to transformed str1 into str2 , otherwise not ..
Driver Code.
Function Call"
Solution in Python:

What is a code to transform string str1 into str2 by taking characters from string str3 and the other steps required?
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#Here is code to transform string str1 into str2 by taking characters from string str3 and the other steps required.
 def convertString ( str1 , str2 , str3 ) :
	freq = { }
	for i in range ( len ( str3 ) ) :
		if ( freq . get ( str3 [ i ] ) == None ) :
			freq [ str3 [ i ] ] = 1
		else :
			freq . get ( str3 [ i ] , 1 )
	ptr1 = 0
	ptr2 = 0 ;
	flag = True
	while ( ptr1 < len ( str1 ) and ptr2 < len ( str2 ) ) :
		if ( str1 [ ptr1 ] == str2 [ ptr2 ] ) :
			ptr1 += 1
			ptr2 += 1
		else :
			if ( freq [ str3 [ ptr2 ] ] > 0 ) :
				freq [ str3 [ ptr2 ] ] -= 1
				ptr2 += 1
			else :
				flag = False
				break
	if ( flag and ptr1 == len ( str1 ) and ptr2 == len ( str2 ) ) :
		print ( " YES " )
	else :
		print ( " NO " )
if __name__ == ' _ _ main _ _ ' :
	str1 = " abyzfe "
	str2 = " abcdeyzf "
	str3 = " popode "
	convertString ( str1 , str2 , str3 )