Python – Test String in Character List and vice-versa

Given a String, check if it’s present in order in the character list and vice versa.

Input : test_str = ‘geeks’, K = [‘g’, ‘e’, ‘e’, ‘k’, ‘f’, ‘o’, ‘r’, ‘g’, ‘e’, ‘e’, ‘k’, ‘s’] [ String in Character list ] 
Output : True 
Explanation : geeks is present in list , starting from 7th index till end.

Input : test_str = ‘geeksforgeeks’, K = [‘g’, ‘e’, ‘e’, ‘k’, ‘s’] [Character list in String] 
Output : True 
Explanation : [‘g’, ‘e’, ‘e’, ‘k’, ‘s’] present in string, starting from the beginning of string. 

Method #1: Using in operator + join() [ String in character list ]

In this, we convert the character list to a string using join() and apply it in the operator to test for substring presence.

Python3

# Python3 code to demonstrate working of
# Test String in Character List and vice-versa
# Using in operator and join() [String in list]

# initializing string
test_str = 'geeks'

# printing original string
print("The original string is : " + str(test_str))

# initializing Character list
K = ['g', 'e', 'e', 'k', 'f', 'o', 'r', 'g', 'e', 'e', 'k', 's']

# joining list
joined_list = ''.join(K)

# checking for presence
res = test_str in joined_list

# printing result
print("Is String present in character list : " + str(res))

Output

The original string is : geeks
Is String present in character list : True

Time Complexity: O(n)
Auxiliary Space: O(n)

Method #2 : Using in operator + join() [ Character List in String ]

In this, the target character list is converted to String and then checked in String using in operator.

Python3

# Python3 code to demonstrate working of
# Test String in Character List and vice-versa
# Using in operator + join() [ Character List in String ]

# initializing string
test_str = 'geeksforgeeks'

# printing original string
print("The original string is : " + str(test_str))

# initializing Character list
K = ['g', 'e', 'e', 'k', 's']

# joining list
joined_list = ''.join(K)

# checking for presence
res = joined_list in test_str

# printing result
print("Is character list present in String : " + str(res))

Output

The original string is : geeksforgeeks
Is character list present in String : True

Time Complexity: O(n) -> as join method takes O(n) complexity
Auxiliary Space: O(n)

Method 3 :  using the set() function and intersection() method

Step-by-step approach:

• Initialize the original string and print it.
• Initialize the character list.
• Convert the character list to a set using the set() function.
• Get the intersection of the character set and the set of the original string using the intersection() method.
• Check if the length of the intersection set is equal to the length of the character set.
• Print the result.

Python3

# Python3 code to demonstrate working of
# Test String in Character List and vice-versa
# Using set() and intersection() [ Character List in String ]

# initializing string
test_str = 'geeksforgeeks'

# printing original string
print("The original string is : " + str(test_str))

# initializing Character list
K = ['g', 'e', 'e', 'k', 's']

# converting list to set
char_set = set(K)

# getting intersection of sets
intersect_set = char_set.intersection(set(test_str))

# checking if all characters are present
res = len(intersect_set) == len(char_set)

# printing result
print("Is character list present in String : " + str(res))

Output

The original string is : geeksforgeeks
Is character list present in String : True

Time complexity: O(n), where n is the length of the original string.
Auxiliary space: O(k), where k is the length of the character list.