SDE - 1

You are given two binary trees with 'n' and 'm' nodes respectively.

You need to return true if the two trees are identical. Otherwise, return false.

Example:

For the trees given below:- 

The given trees are identical as:-
1. The number of nodes in both trees is the same. 
2. The number of edges in both trees is the same. 
3. The data for root for both the trees is the same i.e 5. 
4. The data of root -> left (root’s left child) for both the trees is the same i.e 2.
5. The data of root -> right (root’s right child) for both the trees is the same i.e 3.
6. The data of root -> right -> left ( left child of root’s right child) for both the trees is the same i.e 6.
7. Nodes with data 2 and 6 are the leaf nodes for both the binary trees. 

You have been given string 'S' of length 'N' that may contain duplicate alphabets. Your task is to return the count of distinct subsequences of it.

For example:

For the given string “deed” :
The possible subsequences are {“”}, {“d”}, {“e”}, {“de”}, {“e”}, {“de”}, {“ee”}, {“dee”}, {“d”}, {“dd”}, {“ed”}, {“ded”}, {“ed”}, {“ded”}, {“eed”} and {“deed”}.

As, {“d”}, {“e”}, {“de”}, {“ed”} and {“ded”} are repeated. 

The distinct subsequences are {“”}, {“d”}, {“e”}, {“de”}, {“ee”}, {“dee”}, {“dd”}, {“ed”}, {“ded”}, {“eed”} and {“deed”}

Thus, the output will be 11. 

Note:

As the answer can be large, return your answer modulo 10^9  + 7.  

You have been given a singly Linked List of 'N' nodes with integer data and an integer 'K'.

Your task is to remove the 'K'th node from the end of the given Linked List and return the head of the modified linked list.

Example:

Input : 1 -> 2 -> 3 -> 4 -> 'NULL'  and  'K' = 2
Output: 1 -> 2 -> 4 -> 'NULL'
Explanation:
After removing the second node from the end, the linked list become 1 -> 2 -> 4 -> 'NULL'.

You are given a string ‘expression’ consists of characters ‘+’, ‘-’, ‘*’, ‘/’, ‘(‘, ‘)’ and ‘0’ to ‘9’, that represents an Arithmetic Expression in Infix Notation. Your task is to evaluate this Arithmetic Expression.

In Infix Notation, operators are written in-between their operands.

Note :

1. We consider the ‘/’ operator as the floor division.

2. Operators ‘*’ and ‘/’ expression has higher precedence over operators‘+’ and ‘-’ 

3. String expression always starts with ‘(‘ and ends with ‘)’.

4. It is guaranteed that ‘expression’ represents’ a valid expression in Infix notation.

5. It is guaranteed that there will be no case that requires division by 0.

6. No characters other than those mentioned above are present in the string. 

7. It is guaranteed that the operands and final result will fit in a 32-bit integer.

For example :

Consider string ‘expression’ = ‘((2+3)*(5/2))’. 
Then it’s value after evaluation will be ((5)*(2)) = 10. 

You have been given a string ‘A’ consisting of lower case English letters. Your task is to find the length of the longest palindromic subsequence in ‘A’.

A subsequence is a sequence generated from a string after deleting some or no characters of the string without changing the order of the remaining string characters. (i.e. “ace” is a subsequence of “abcde” while “aec” is not).

A string is said to be palindrome if the reverse of the string is the same as the actual string. For example, “abba” is a palindrome, but “abbc” is not a palindrome.

You have been given two arrays, 'AT' and 'DT', representing the arrival and departure times of all trains that reach a railway station.

Your task is to find the minimum number of platforms required for the railway station so that no train needs to wait.

Note :

1. Every train will depart on the same day and the departure time will always be greater than the arrival time. For example, A train with arrival time 2240 and departure time 1930 is not possible.

2. Time will be given in 24H format and colons will be omitted for convenience. For example, 9:05AM will be given as "905", or 9:10PM will be given as "2110".

3. Also, there will be no leading zeroes in the given times. For example, 12:10AM will be given as “10” and not as “0010”.