The first difference is the syntax. Other than that, the major differences are:
C++
* OOP is optional.
* Compiled: produces non-portable native code.
* Manually managed memory. Garbage collection libraries are available.
* Source can be written to be portable, so a correctly written program can be compiled for any platform where a C++ compiler is available.
* Mostly used for medium-to-high performance applications, such as games.
Daily Archives: October 4, 2015
How database indexing works?
Why is it needed?
When data is stored on disk based storage devices, it is stored as blocks of data. These blocks are accessed in their entirety, making them the atomic disk access operation. Disk blocks are structured in much the same way as linked lists; both contain a section for data, a pointer to the location of the next node (or block), and both need not be stored contiguously.
Due to the fact that a number of records can only be sorted on one field, we can state that searching on a field that isn’t sorted requires a Linear Search which requires N/2 block accesses (on average), where N is the number of blocks that the table spans. If that field is a non-key field (i.e. doesn’t contain unique entries) then the entire table space must be searched at N block accesses.
Whereas with a sorted field, a Binary Search may be used, this has log2 N block accesses. Also since the data is sorted given a non-key field, the rest of the table doesn’t need to be searched for duplicate values, once a higher value is found. Thus the performance increase is substantial.
Static vs Volatile in Java
Declaring a static variable in Java, means that there will be only one copy, no matter how many objects of the class are created. The variable will be accessible even with no Objects created at all. However, threads may have locally cached values of it.
When a variable is volatile and not static, there will be one variable for each Object. So, on the surface it seems there is no difference from a normal variable but totally different from static. However, even with Object fields, a thread may cache a variable value locally.
This means that if two threads update a variable of the same Object concurrently, and the variable is not declared volatile, there could be a case in which one of the thread has in cache an old value.
Even if you access a static value through multiple threads, each thread can have it’s local cached copy! To avoid this you can declare the variable as static volatile and this will force the thread to read each time the global value.
However, volatile is not a substitute for proper synchronisation! For instance:
Maximum number of overlapping intervals – Merge Overlapping Intervals – Max Task Load
Given a set of intervals, how do we find the maximum number of intervals overlapping at any point of time.
For example – { (0,2), (3, 7), (4,6), (7,8), (1,5) }. The maximum number of intervals overlapped is 3 during (4,5).
Floor and Ceiling of a Key in Sorted Array – Search Min Diff Element
Given a sorted array and a value x, the ceiling of x is the smallest element in array greater than or equal to x, and the floor is the greatest element smaller than or equal to x. Assume than the array is sorted in non-decreasing order. Write efficient functions to find floor and ceiling of x.
Weighted job/interval scheduling – Activity Selection Problem
Given N jobs where every job is represented by following three elements of it.
1) Start Time
2) Finish Time.
3) Weight representing Profit or Value Associated.
Find the maximum profit subset of jobs such that no two jobs in the subset overlap.