Instead of counting all unique characters and struggling with all possible substrings,
we can count for every char in S, how many ways to be found as a unique char.
We count and sum, and it will be out answer.

Let, index[26][2] record last two occurrence index for every upper characters.
1) Initialise all values in index to -1.
2) Loop on string S, for every character c, upda...

Approach 1 : 

Every position in the string has a depth - some number of matching parentheses surrounding it. For example, the dot in (()(.())) has depth 2, because of these parentheses: (__(.__))

1) Our goal is to maintain the score at the current depth we are on. 
2) When we see an opening bracket, we increase our depth, and our score at the new depth is 0. 
...

Demand paging is a method that loads pages into memory on demand. This method is mostly used in virtual memory. In this, a page is only brought into memory when a location on that particular page is referenced during execution. The following steps are generally followed:

1) Attempt to access the page.
2) If the page is valid (in memory) then continue processing instructions as normal....

We will preorder to generate TreeNodes, push them to the stack and perform postorder to pop them out.

1) Iterate on pre array and construct node one by one.
2) Stack saves the current path of the tree.
3) node = new TreeNode(pre[i]), if not left child, add node to the left. otherwise add it to the right.
4) If we meet a same value in the pre and post, it means we have completed ...

This problem was actually a variation Unbounded Kanpsack Problem . I first gave the interviewer a naive recursive
approach and then later optimised it using memoisation .

Naive Recursive Approach :

1) Create a recursive function ( int minCost(cost, idx , w) ) which returns the optimal answer for an array which starts
with index idx and for a given weight w.

2) Now for...

Tip 1 : The cross questioning can go intense some time, think before you speak.
Tip 2 : Be open minded and answer whatever you are thinking, in these rounds I feel it is important to have opinion.
Tip 3 : Context of questions can be switched, pay attention to the details. It is okay to ask questions in these round,
like what are the projects currently the company is investing, which te...