Cracking the Coding Interview, 4 Edition - 150 Programming Interview Questions and Solutions

Chapter 5 | Bit Manipulation
How to Approach:
Bit manipulation can be a scary thing to many candidates, but it doesn’t need to be! If you’re
shaky on bit manipulation, we recommend doing a couple of arithmetic-like problems to
boost your skills. Compute the following by hand:
1010 - 0001 1010 + 0110 1100^1010
1010 > 1 0xFF - 1 0xAB + 0x11
If you’re still uncomfortable, examine very carefully what happens when you do subtraction,
addition, etc in base 10. Can you repeat that work in base 2?
NOTE: The Windows Calculator knows how to do lots of operations in binary,
including ADD, SUBTRACT, AND and OR. Go to View > Programmer to get into
binary mode while you practice.
Things to Watch Out For:
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It’s really easy to make mistakes on these problems, so be careful! When you’re writing
code, stop and think about what you’re writing every couple of lines - or, better yet, test
your code mid-way through! When you’re done, check through your entire code.
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If you’re bit shifting, what happens when the digits get shifted off the end? Make sure
to think about this case to ensure that you’re handling it correctly.
And (&): 0 & 0 = 0 1 & 0 = 0 0 & 1 = 0 1 & 1 = 1
Or (|): 0 | 0 = 0 1 | 0 = 1 0 | 1 = 1 1 | 1 = 1
Xor (^): 0 ^ 0 = 0 1 ^ 0 = 1 0 ^ 1 = 1 1 ^ 1 = 0
Left Shift:
x > 2 = 00000110
00011001 >> 4 = 00000001
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Cracking the Coding Interview | Concepts and Algorithms