interview question answers continued

Q: In Java differentiate between final, finally and finalize ?
A: The keyword final in Java are used to denote that which cannot be inherited further. The finally is used for mandatory invocation after try catch exception handling and the finalize is used by the runtime for garbage collection of objects.

Q. Given two arrays, how will you find the intersection ?
A. If intersections is defined as the set of elements that appear in both arrays in no particular order, and both the arrays can be arbitrarily large or have elements from an arbitrary range, then one approach could be to sort both arrays and walk down both arrays element by element and put the common ones in a bag until one of the arrays gets over.

Q. Given two squares by their four corners coordinates, find the coordinates of their intersection.
A. Take the minimum and maximum of all x coordinates and the same for y coordinates. If these are of the same square, one is contained in the other. Otherwise they are either overlapping or disjoint, which you can tell from the diagnoally opposite ends of the min and max. If they do overlap, we already have the co-ordinates for two diaognally opposite corners and other two are common points to both squares.

Q. What is the difference between a hash table and a hash map.
A. A hash table stores values based on the hash computed from the value. A hash map stores key value pairs based on the hash of the key.  In C++ a hash map is used where < is not defined or unsuitable for the intended key.   A good hash function is a pre-requisite for both or there can be collisions for some entries.   For example :
template<class T> size_t Hash<T>::operator() (const T& key) const
{
size_t ers = 0;
size_t len = sizeof(T);
const char* p = reinterpret_case<const char*> (&key);
while (len--) res = (res << 1) ^*p++;
return res;
}

Q: What is the significance of the term "dead beef"
A: Initialized memory is usually set to 0xEF bit pattern to indicate the object at this memory has not been used. Similarly 0xCC is used to denote uninitialized memory or no man's land.

Q: Write a C code to find the depth of a binary tree.
A: int GetDepth(Node* root)
     {
       if (root == null) return 0;
       int depth = 1;
       if (root->left == null && root->right == null) return depth;
       int subtree = GetDepth(root->left);
       if (subtree >= depth) depth = subtree+ 1;
       subtree = GetDepth(root->right);
       if(subtree >= depth) depth = subtree + 1;
       return depth;
     }