human
Check if string S1 can be formed using repeated insertions of another string S2 | Function to check a valid insertion.
Store the size of string.
Maintain a stack for characters.
Iterate through the string.
push the current character on top of the stack.
If the current character is the last character of string S2 then pop characters until S2 is not formed.
index of last character of the string S2.
pop characters till 0 - th index.
Check if stack in non - empty.
Driver Code"
How can the above be solved in Python?

What is a code to check if string S1 can be formed using repeated insertions of another string S2 and the other steps required?
assistant
#Here is code to check if string S1 can be formed using repeated insertions of another string S2 and the other steps required.
 def validInsertionstring ( S1 , S2 ) :
	N = len ( S1 )
	M = len ( S2 )
	st = [ ]
	for i in range ( N ) :
		st . append ( S1 [ i ] )
		if ( S1 [ i ] == S2 [ M - 1 ] ) :
			idx = M - 1
			while ( idx >= 0 ) :
				if ( len ( st ) == 0 ) :
					return False
				c = st [ - 1 ]
				st . pop ( )
				if ( c != S2 [ idx ] ) :
					return False
				idx -= 1
	if ( len ( st ) != 0 ) :
		return False
	else :
		return True
S1 = " aabb "
S2 = " ab "
if validInsertionstring ( S1 , S2 ) :
	print ( " Yes " )
else :
	print ( " No " )