Shantibhushan Naik

Category: Education

  • Brainteasers

    1. How many degrees angle between hour, minute hand when time is 3:15?
      7.5°
      360° full circle, therfore (360°/12 hrs) = 30° /hour.
      At 3:15,  minutes hand points to the 3, hour hand is ahead of 3 by 1/4th (15/60),  which is 7.5° apart. (30°/4)=7.5°
    2. Why are manhole covers round?
      – Round covers can be easily rotated
      – It’s easier to dig a circular hole
      – Round castings are easier to machine using a lathe
      – Easier to manufacture than custom-made covers
    3. How will you generate random number between two given numbers
      Assuming n1, n2 random number between them would be n1 + Math.random() * (n2 – n1)
    4. How will you sort a million integers?
      Split them into meaningful subsets, sort each subset, merge subset back
      http://neopythonic.blogspot.com/2008/10/sorting-million-32-bit-integers-in-2mb.html
    5. How many windows will be open in a 100 window room if you go around  a 100 times toggling each window you come across? All windows are closed initially.
      100 windows,  all closed.
      1st round, you toggle all windows i.e. all windows are opened
      2nd round, you close all even-numbered windows – 2, 4, 6, …
      3rd round, you open, close odd numbered winodws – 3, 6, 9,…
      So after 100 times, windows open are windows who have been toggled odd number of times. For e.g. consider window 12, round 1 will make it open, 2 will make it closed, 3 will make it open, 4 closed, then directly 12 will make it open. Consider again, window 20 – 1 (open), 2 (close), 4 (open), 5 (close), 10 (open), 20 (close). Consider 7 – 1 (open), 7 (close). So window 12 got touched 5 times, window 20 got touched 6 times, window 7 touched 2 times.
      So, in order to find “open” windows between 1-100, we have to find number having “odd” number of factors, which means numbers who have one repeated factor i.e.  factor by same factor gives the number e.g. 16 has 1, 2, 4, 8, 16 – open window. It has 4 which means 4×4= 16. Consider 20 has 1, 2, 4, 5, 10, 20. No factor is repetitive.
      Therefore, let us find numbers which are below 100, but are having square products, similar to 4×4 = 16 starting with 1, which gives 12=1, 22=4, 32=9, 42=16, 52=25, 62=36, 72=49, 82=64, 92=81, 102=100
      So open windows are 1, 4, 9, 16, 25, 36, 49, 64, 81, 100 = 1o open windows
    6. A party of four travelers comes to a rickety bridge at night. The bridge can hold the weight of at most two of the travelers at a time, and it cannot be crossed without using a flashlight. The travelers have one flashlight among them. Each traveler walks at a different speed: The first can cross the bridge in 1 minute, the second in 2 minutes, the third in 5 minutes, and the fourth takes 10 minutes to cross the bridge. If two travelers cross together, they walk at the speed of the slower traveler. What is the least amount of time in which all the travelers can cross from one side of the bridge to the other?
      Obvious (but incorrect)
      Incorrect answer

      Not  so obvious (correct answer)
      Correct answer

    7. Next…

    A party of four travelers comes to a rickety bridge at night. The bridge can hold the weight of at most two of the travelers at a time, and it cannot be crossed without using a flashlight. The travelers have one flashlight among them. Each traveler walks at a different speed: The first can cross the bridge in 1 minute, the second in 2 minutes, the third in 5 minutes, and the fourth takes 10 minutes to cross the bridge. If two travelers cross together, they walk at the speed of the slower traveler.

    What is the least amount of time in which all the travelers can cross from one side of the bridge to the other?

  • https in 5 easy steps

    Simple 5 step guide to setting up https with your own self-signed certificate
    Prerequisites: Apache2, Ubuntu Server

    1. Generate local keypair
      /usr/bin/openssl genrsa -des3 -out {your domain name}.key 3072
    2. Create self-signed certificate
      /usr/bin/openssl req -new -key {your domain name}.key -x509 -out {your domain name}.crt
    3. Configure your host on port 443 to use the certificate
      <VirtualHost {your ip}:443>
      ...
      SSLEngine on
      SSLCertificateFile {path where certificate is}/{your domain name}.crt
      SSLCertificateKeyFile {path where key file is}/{your domain name}.key
      SetEnvIf User-Agent ".*MSIE.*" nokeepalive ssl-unclean-shutdown
      ...
      </VirtualHost>
    4. Optional: If you do not want to enter key password each you restart Apache, you can embed the password in key itself.
      /usr/bin/openssl rsa -in       {path where key file is}/{your domain name}.key -out {path where key file is}/{your domain name}.key.nopass
      Remember to update your Apache configuration to use the new file
      # SSLCertificateKeyFile {path where key fileis}/{your domain name}.key
      SSLCertificateKeyFile {path where key file is}/{your domain name}.key.nopass
    5. That’s it view it. Restart your apache to load the new configuration. And try accessing your url with https://

    If you receive a certificate warning, simply accept it, and proceed. Congratulations, your communication is now encrypted, and safe from prying eyes!

    Self-signed certificate

    [Translate]

  • Colors to your life

    Very often we are impressed with awe when we see a beautiful picture, photo, advert. The colors, their combination presents an alluring view just right for our eyes. If you notice more closer, you can seeing that more often the colors are complemented (red with white, green with blue…) to give a undistracted overall look. This is essentially because our eyes find this visually pleasant.

    I have a tool which can offer such combinations, and you should design your color combinations using the suggested patterns

    http://9i9.me/colors/index.html/ – For visually stunning color combinations

    Keep working!

  • Interesting alternatives to databases in opensource

    I stumbled upon this url. The list of various options on databases is pretty amazing.

    http://www.webresourcesdepot.com/25-alternative-open-source-databases-engines/

    It’s a definite read. I never knew so many existed.

  • Japanese samurai language

    Japanese language is often interesting, when it comes to dialects. Try out standard Japanese into many other (un)known dialects here.

  • Tired of teaching how to think

    Sir Ernest Rutherford, President of the Royal Academy, and recipient of the Nobel Prize in Physics, related the following story:

    “Some time ago I received a call from a colleague. He was about to give a student a zero for his answer to a physics question, while the student claimed a perfect score. The instructor and the student agreed to an impartial arbiter, and I was selected.

    I read the examination question: “Show how it is possible to determine the height of a tall building with the aid of a barometer.”

    The student had answered: “Take the barometer to the top of the building,attach a long rope to it, lower it to the street, and then bring it up, measuring the length of the rope. The length of the rope is the height of the building.”

    The student really had a strong case for full credit since he had really answered the question completely and correctly! On the other hand, if full credit were given, it could well contribute to a high grade in his physics course and certify competence in physics, but the answer did not confirm this. I suggested that the student have another try. I gave the student six minutes to answer the question with the warning that the answer should show some knowledge of physics.

    At the end of five minutes, he hadn’t written anything. I asked if he wished to give up, but he said he had many answers to this problem; he was just thinking of the best one. I excused myself for interrupting him and asked him to please go on. In the next minute, he dashed off his answer, which read: “Take the barometer to the top of the building and lean over the edge of the roof. Drop the barometer, timing its fall with a stopwatch.

    Then, using the formula x=0.5*a*t^2, calculate the height of the building.”

    At this point, I asked my colleague if he would give up. He conceded, and gave the student almost full credit. While leaving my colleague’s office, I recalled that the student had said that he had other answers to the problem, so I asked him what they were.

    “Well,” said the student, “there are many ways of getting the height of a tall building with the aid of a barometer. For example, you could take the barometer out on a sunny day and measure the height of the barometer, the length of its shadow, and the length of the shadow of the building, and by the use of simple proportion, determine the height of the building.”

    “Fine,” I said, “and others?”

    “Yes,” said the student, “there is a very basic measurement method you will like. In this method, you take the barometer and begin to walk up the stairs. As you climb the stairs, you mark off the length of the barometer along the wall. You then count the number of marks, and his will give you the height of the building in barometer units.”

    “A very direct method.”

    “Of course. If you want a more sophisticated method, you can tie the barometer to the end of a string, swing it as a pendulum, and determine the value of g [gravity] at the street level and at the top of the building.

    From the difference between the two values of g, the height of the building, in principle, can be calculated.”

    “On this same tack, you could take the barometer to the top of the building, attach a long rope to it, lower it to just above the street, and then swing it as a pendulum. You could then calculate the height of the building by the period of the precession”.

    “Finally,” he concluded, “probably the best,” he said, “is to take the barometer to the basement and knock on the superintendent’s door. When the superintendent answers, you speak to him as follows: ‘Mr. Superintendent, here is a fine barometer. If you will tell me the height of the building, I will give you this barometer.”

    At this point, I asked the student if he really did not know the conventional answer to this question. He admitted that he did, but said that he was fed up with high school and college instructors trying to teach him how to think.

    The name of the student was…

    Neils Bohr

    The Nobel Prize winner in Physics 1922

  • TOYOTA: Speech by Akio Toyoda – president of Toyota Motor Corporation

    “Contributing to society” at Toyota means two things.  First, it means, “to manufacture automobiles that meet the needs of society and enrich people’s lives.”  And second, “to take root in the communities we serve by creating jobs, earning profits and paying taxes, thereby enriching the local economies where we operate.”

    TOYOTA: Company > Company Profile > Message from Top Management.

  • Management Pros Share Their Secrets

    Remember way back when – when you got your first management job. What do you wish someone had told you then? What would be the one tip you would give to a manager just starting out?

    Management Pros Share Their Secrets.

  • Russian Peasant Multiplication

    Start by writing the two numbers to be multiplied at the head of two columns. Then they repeatedly divide the number in the left column by two (dropping any remainder) and double the number in the right column, writing the two new numbers immediately below their predecessors, until the number in the left column is one. Then they cross out all rows where the number in the left column is even, and add the remaining numbers in the right column, which is the desired product.

    For instance, the product eighteen times twenty-three is found like this.
    Russian Peasant Multiplication
    Programming Praxis: Russian Peasant Multiplication – The Daily WTF.

  • Oscar’s Multi-Monitor taskBar

    Oscar’s Multi-Monitor taskBar.

    Superb in what is says – adds an independent taskbar to each monitor in a multimonitor setup.

    Worth the download.