Ebay Interview Question for Software Engineer / Developers


Country: United States
Interview Type: Phone Interview




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of 2 vote

Hashcode is generated using hashfunctions. We have different hash functions available, you can simply wiki about it.
Hash functions generate a hash key, we use that hash key as an index to store data in the hash table. But what if two objects have same hash values?
To solve this, one way is to create chain of pointers in one bucket.

Suppose you have three values v1, v2, v3.
Hash values are : h(v1) = 0, h(v2)=1, h(v3) = 0

Hash Table:
[0] -> v1 -> v3
[1] -> v1

This solution works fine for less number of collisions, but when number of collisions grow high, the search starts taking ~ O(n)

Another solution is, Open Addressing:
In this method, if some collision occurs, then instead of making a chain in the bucket, we find next available location in the same hash table, and then we store our value there.

For the example above:
[0] -> v1
[1] -> v2
[2] -> v3

We also have different type of methods to search next available position in the hash table.
1. Linear Probing: if the hash value is h and it collides then check at h+1
2. Quadratic Probing: if the hash value is h and it collides then increase the hash by 1^2, 2^2 , 3^2 and so on.

I think this should suffice.

- HauntedGhost March 07, 2013 | Flag Reply


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