Yahoo Placement Paper

I had given this test one month back and unfortunately forget few questions but let me try what I can do -
I knew it that yahoo gives subjective paper and they do give good questions as told by my seniors and as I came to know from other friends in various NIT's.
So as expeccted, Yahoo's paper was semi-subjective in nature where you had to solve on the question paper itself. The first 4-5 questions were aptitude questions. Some of them were like -
A king has been poisoned and one of the 1000 bottles is having poison. You need to find which bottle by "using" the prisoners. The answer is log n I think. Please search in the puzzle section here, I had seen the question. Than there is another famous question of ccubes once. If you have one cube of length 4 painted red, and if it cut down into smaller cubes of size 1 than how many cubes have NO side painted ? well answer is 8 and the forumulae is for a cube of size n, the no. of cubes with no side painted will be [(n-2)^3](n-2 to the power of 3)
Another question was two trains are coming to each other on same track and are 1000 m apart and a bird starts flying from one train to another to and fro i.e first to seond to first to second so how much distance it covered before the trains collided ?
Than there were around 15 questions on programming.Almost all of them were on Hash,heaps and data structures. Make sure that you are very clear with Hash'es and Heaps otherwise there is no way you can clear yahoo. I have always seen that thsoe who gets highest in written in any test ahve advantage over thsoe who clears the cut off marginally.
Than there were around 10 questions on Unix which I screwed pretty badly. The questions were not that tough but my shell scripting was not good. They had asked "how will you dierct the output to this terminal" and similar questions. Some of the questions were related to file handling and Grep. Make sure you are comfortable with unix shell scripting(follow some book with a higher level than of Kanetkar)
Than in the end, there were 2-3 database questions on SQL. You had been given two tables and were asked to write queries on given statement. Since there was EQUI JOIN and LEFT JOIN operations also involved in the statement so I couldn't do those two questions either.
Needless to say, I couldn't clear written exam. The only advice that I can give you is make sure you are good in advance Data Structures as well as in Database and Unix.