## Pairwise swap adjacent nodes of a linked list

Given a linked list, pairwise swap its adjacent nodes. The swapping of data is not allowed, only links should be changed.

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Given a linked list, pairwise swap its adjacent nodes. The swapping of data is not allowed, only links should be changed.

In this post, we will see the difference between Depth first search (DFS) and Breadth first search (BFS) algorithm which are used to traverse/search tree or graph data structure.

In this post, we will discuss how to efficiently implement two stacks in a single array.

Given a BST, count subtrees in it whose nodes lies within a given range. For example, consider below BST. The number of subtrees with nodes in the range [5, 20] are 6.

Given a linked list which can grow in both horizontal and vertical directions (right and down), flatten it into a sorted singly linked list provided that each horizontal and vertical list is already sorted.

Given a stair case, find total number of ways to reach the n’th stair from bottom of the stair when a person is only allowed to climb either 1 or 2 or 3 stairs at a time.

Given a dictionary of ancient origin where the words are arranged alphabetically, find the correct order of alphabets in the ancient language.

Write an efficient algorithm to construct a Cartesian tree from in-order traversal. A Cartesian tree is a binary tree with the heap property: the parent of any node has smaller value than the node itself.

Given a distinct sequence of keys which represents postorder traversal of a binary search tree, construct the tree from the postorder sequence.

Given a distinct sequence of keys which represents preorder traversal of a binary search tree (BST), construct the tree from the postorder sequence.

Given a linked list of strings, check whether concatenation of all values in the list together forms a palindrome. It is not permissible to construct a string out of the linked list nodes and check that string for palindrome.

Given a M x N boggle board, find list of all possible words that can be formed by a sequence of adjacent characters on the the board.