SDE - 1

You are given a string 'exp' which is a valid infix expression.

Convert the given infix expression to postfix expression.

Note:

Infix notation is a method of writing mathematical expressions in which operators are placed between operands. 

For example, "3 + 4" represents the addition of 3 and 4.

Postfix notation is a method of writing mathematical expressions in which operators are placed after the operands. 

For example, "3 4 +" represents the addition of 3 and 4.

Expression contains digits, lower case English letters, ‘(’, ‘)’, ‘+’, ‘-’, ‘*’, ‘/’, ‘^’. 

Example:

Input: exp = ‘3+4*8’

Output: 348*+

Explanation:
Here multiplication is performed first and then the addition operation. Hence postfix expression is  3 4 8 * +.

You are given an undirected, connected and weighted graph G(V, E), consisting of V number of vertices (numbered from 0 to V-1) and E number of edges.

Find and print the total weight of the Minimum Spanning Tree (MST) using Kruskal's algorithm.

By definition, a minimum weight spanning tree is a subset of the edges of a connected, edge-weighted undirected graph that connects all the vertices together, without any cycles and with the minimum possible total edge weight.

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.

Ninja Coin is a famous crypto-currency in Ninja Land. Ninja has an array/list ‘PRICE’ of size ’N’ where ‘PRICE[i]’ is the price of a Ninja Coin on an ith day in INR, where 0 <= 'i' <= N-1.

The span of the Ninja Coin price on an ith day is defined as the maximum number of consecutive days (starting from the ith day and going backward) for which the price of a Ninja Coin was less than or equal to its price at ith day.

Your task is to return an array/list of size ‘N’ where the ith integer is the span of Ninja Coin price on an ith day. Go through the example for more clarity.

For Example :

Let the price of Ninja Coin for 5 consecutive days is [4, 2, 3, 3, 7].

Then the span of Ninja Coin on the 0th day is 1 because we cannot move backward from day 0.

The span of Ninja Coin on the 1st day is 1 because the price on day 0 is 4 which is greater than 2, so the only day 1 is counted.

The span of Ninja Coin on the 2nd day is 2 because the price on day 2 and day 1 is less than or equal to 3 and then on day 0 price is 4 which is greater than 3, so we count day 2 and day 1.

The span of Ninja Coin on the 3rd day is 3 because the price on day 3, day 2, and day 1 is less than or equal to 3, and on day 0 price is 4 which is greater than 3, so we count day 3, day 2, and day 1.

The span of Ninja Coin on the 4th day is 5 because its value is higher than all previous days values.    

Thus you should return an array/list [1, 1, 2, 3, 5].

Given a Binary Tree, convert this binary tree to a Doubly Linked List.

A Binary Tree (BT) is a data structure in which each node has at most two children.

A Doubly Linked List contains a previous pointer, along with the next pointer and data.

The order of nodes in Doubly Linked List must be the same as Inorder of the given Binary Tree.

The doubly linked list should be returned by taking the next pointer as right and the previous pointer as left.

You need to return the head of the Doubly Linked List.

For the given binary tree :

You need to return the head to the doubly linked list.
The doubly linked list would be: 1 2 3 4 5 and can be represented as:

Design and implement a data structure for Least Recently Used (LRU) cache to support the following operations:

1. get(key) - Return the value of the key if the key exists in the cache, otherwise return -1.

2. put(key, value), Insert the value in the cache if the key is not already present or update the value of the given key if the key is already present. When the cache reaches its capacity, it should invalidate the least recently used item before inserting the new item.

You will be given ‘Q’ queries. Each query will belong to one of these two types:

Type 0: for get(key) operation.
Type 1: for put(key, value) operation.

Note :

1. The cache is initialized with a capacity (the maximum number of unique keys it can hold at a time).

2. Access to an item or key is defined as a get or a put operation on the key. The least recently used key is the one with the oldest access time.