Function to create prefix array
def preCompute ( n , s , pref ) : NEW_LINE INDENT for i in range ( 1 , n ) : NEW_LINE INDENT pref [ i ] = pref [ i - 1 ] NEW_LINE if s [ i - 1 ] == s [ i ] : NEW_LINE INDENT pref [ i ] += 1 NEW_LINE DEDENT DEDENT DEDENT