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 array 'ARR' of 'N' integers and you have to calculate 3 things for the given array:-

1. Mean - function mean(): This function should calculate the mean of the array.

2. Median - function median(): This function should calculate the median of the array.

3. Mode - function mode(): This function should calculate the mode of the array.

Note :

It can be shown that Mean and Median is in the form of P/Q, where P and Q are coprime integers and Q != 0. You need to return P and Q.

For Mode, if the highest frequency of more than one element is the same, return the smallest element.

For Example, for the given array {1, 1, 2, 2, 3, 3, 4}, the mode will be 1 as it is the smallest of all the possible modes i.e 1, 2 and 3.

You are given a Doubly Linked List of integers and a positive integer 'K' representing the group size. Modify the linked list by reversing every group of 'K' nodes in the linked list.

A doubly linked list is a type of linked list that is bidirectional, that is, it can be traversed in both directions, forward and backward. 

Note:

If the number of nodes in the list or in the last group is less than K, just reverse the remaining nodes. 

Example:

Linked list: 8 9 10 11 12
K: 3 

Output: 10 9 8 12 11

We reverse the first K (3) nodes. Now, since the number of nodes remaining in the list (2) is less than K, we just reverse the remaining nodes (11 and 12).  

Ninja started a gaming shop and for that shop, he is planning to make a new game ‘String Ka Khel’. In that game user is provided with ‘N’ number of strings and he has to find out the maximum length of strings he can form by joining these ‘N’ strings. For joining two strings there is a condition that two strings will only join if the last character of the first string is same as the last character of the second string. If the user will find out the correct answer he will be given Coding Ninja goodies by the Ninja.

So your task is to find the maximum length of string which can be formed by joining strings according to the given condition. If no such combination exists return ‘0’. Strings only contain the letter ‘B’ and ‘R’.

Example:

The string is ‘RR’, ‘RB’ so we can combine ‘RR’ and ‘RB’ as the last character of ‘RR’ i.e ‘R’ matches with the first character of ‘RB’. But we cant combine ‘RB’ and ‘RR’ as the last character of ‘RB’ i.e ‘B’ doesn't matches with the first character of ‘RR’ i.e ‘R’ so our answer is '4'.

You are given an array consisting of N integers, and an integer, K. Your task is to determine the total sum of the minimum element and the maximum element of all subarrays of size K.

Note :

The array may contain duplicate elements.
The array can also contain negative integers.
The size of the array is at least 2.
There exists at least one such subarray of size k.

Aakash is a member of Ninja club. He has a weird family structure. Every male member (M) gives birth to a male child first and then a female child, whereas every female (F) member gives birth to a female child first and then to a male child. Aakash analyses this pattern and wants to know what will be the Kth child in his Nth generation. Can you help him?

A sample generation tree is shown, where ‘M’ denotes the male member and ‘F’ denotes the female member. 

Note

The generation tree starts with a male member i.e. Aakash. 
Every member has exactly two children. 
The given N and K will always be valid. 

You have been given an array/list ‘ARR’ consisting of ‘N’ positive integers. Your task is to return the Next Greater Element(NGE) for every element.

The Next Greater Element for an element ‘X’ is the first element on the right side of ‘X’ in the array 'ARR', which is greater than ‘X’. If no such element exists to the right of ‘X’, then return -1.

For example:

For the given array 'ARR' = [7, 12, 1, 20]

The next greater element for 7 is 12.
The next greater element for 12 is 20. 
The next greater element for 1 is 20. 
There is no greater element for 20 on the right side.

So, the output is [12, 20, 20, -1].