SDE - 1

You are given a singly linked list ‘HEAD’ consisting of ‘N’ nodes. The task is to group all the odd nodes together, followed by the even nodes, maintaining the relative order of nodes given in the input. Note that we are talking about the node’s positions and not the value stored in the node. Try to write an in-place algorithm (i.e., without using any extra space) to solve this problem.

Example:

Given linked list: ‘2 => 1 => 3 => 4 => 6 => 5’

While maintaining the relative order of nodes as it is in the input, Nodes at odd positions are (2, 3, 6), and nodes at evens position are (1, 4, 5).

Modified linked list: ‘2 => 3 => 6 => 1 => 4 => 5’

Note:

1. Consider that the first node is odd, the second is even, and so on.

The lowest common ancestor (LCA) is a concept in graph theory and computer science.

Let ‘T’ be a rooted tree with ‘N’ nodes. The lowest common ancestor is defined between two nodes, ‘u’ and ‘v’, as the lowest node in ‘T’ that has both ‘u’ and ‘v’ as descendants (where we allow a node to be a descendant of itself). - Wikipedia

For the given tree, The LCA of nodes 5 and 8 will be node 2, as node 2 is the first node that lies in the path from node 5 to root node 1 and from node 8 to root node 1.

Path from node 5 to root node looks like 5 → 2 → 1.

Path from node 8 to root node looks like 8 → 6 → 2 → 1.

Since 2 is the first node that lies in both paths. Hence LCA will be 2.

Given any two nodes ‘u’ and ‘v’, find the LCA for the two nodes in the given Tree ‘T’.

Note: For each test case, the tree is rooted at node 1.

You are given a string 'str' and an integer 'D'. Your task is to rotate the given string left (anticlockwise) and right (clockwise) by 'D' units from the starting index. You are required to return the rotated string.

Example :

Given a directed graph, check whether the graph contains a cycle or not. Your function should return true if the given graph contains at least one cycle, else return false.