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# Python | Check if the list is in another list

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Examples :

`  Input:  A = [1, 2], B = [1, 2, 3, 1, 1, 2 , 2]  Output:  True  Input:  A = [’x’,’ y’, ’z’], B = [’ x’, ’a’,’ y’, ’x’,’ b’, ’z’]  Output:  False `

Approach # 1: Naive Approach

Simple naive approach — use two for loops and check if the whole list A is contained in list B or not. If such a position occurs in list A, then break the loop and return true, otherwise false

 ` # Python3 list checker ` ` # contained in another list without breaking order `   ` def ` ` removeElements (A, B): ` ` for ` ` i ` ` in ` ` range ` ` (` ` len ` ` (B) ` ` - ` ` len ` ` (A) ` ` + ` ` 1 ` `): ` ` for ` ` j ` ` in ` ` range ` ` (` ` len ` ` (A)): ` ` if ` ` B [i ` ` + ` ` j]! ` ` = ` ` A [j]: ` ` break ` ` else ` `: ` ` return ` ` True ` ` return ` ` False ` ` `  ` # Driver code ` ` A < / code> = [ 1 , 2 ] `` B = [ 1 , 2 , 3 , 1 , 1 , 2 , 2 ] print (removeElements (A, B)) `

Exit :

` True `

Approach # 2: Understanding the List

A more effective approach is to use the Comprehension List. First we initialize n with length A. Now we use a for loop to len (B) -n and check in each iteration if ` A == B [i: i + n] ` or not.

 ` # Python3 program to remove elements ` ` # list that repeats less than k times `   ` def ` ` removeElements (A, B): ` ` n ` ` = ` ` len ` ` (A) ` ` return ` ` any ` ` (A ` ` = ` ` = ` ` B [i: i ` ` + n] for i in range ( len (B) - n + 1 )) ``     # Driver code A = [ 1 , 2 ] B = [ 1 , 2 , 3 , 1 , 1 , 2 , 2 ] print (removeElements (A, B) ) `

Exit:

` True `

Approach # 3: Using the join module and map

Here we use the join , to concatenate both lists into strings and then use the in operator to check if list A is contained in B or not.

 ` # Python3 program for removing elements ` ` # a list that repeats less than k times `  < / p>   ` def ` ` removeElements (A , B): ` ` return ` ` ’ , ’` `. join (` ` map ` ` (` ` str ` `, A)) ` ` in ` ` ’,’ ` `. join (` ` map ` ` (` ` str ` `, B)) ` ` `  ` # Driver code ` ` A ` ` = ` ` [` ` ’x’ ` `, ` `’ y’ ` `, ` ` ’z’ ` `] ` ` B ` ` = ` ` [` ` ’x’ ` `, ` `’ a’ ` `, ` `’ y’ ` `, ` ` ’x’ ` `, ` ` ’b’ ` `, ` ` ’z’ ` `] ` ` print ` ` (removeElements (A, B)) `

Exit:

` False `

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