Dutch Flag problem

Dutch flag is a notable problem wherein you have a array representing three colors . Red(R), Green(G) and Blue(B) which needs to be sorted with Reds coming first followed by Green and then Blue. This is achieved by lumoto partitioning scheme.

Printing out all combinations of string

Printing out all combinations of a string

Printing out all the permutations of string

How to generate permutation of a given string where digits are kept as it is, but alphabets are replaced by lower and upper case characters The above solution uses immutable strings so its not efficient time complexity-wise below solution replaces string with list

Palindrome Linked List

Given the head of a singly linked list, return true if it is a palindrome. 

 Example 1: Input: head = [1,2,2,1] 

Output: true 

Example 2: Input: head = [1,2]

 Output: false 

 Constraints: The number of nodes in the list is in the range [1, 105]. 0 <= Node.val <= 9 

 Follow up: Could you do it in O(n) time and O(1) space?