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Why does ~True result in -2?
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int(True) is 1.
1 is:
00000001
and ~1 is:
11111110
Which is -2 in Two's complement1
1 Flip all the bits, add 1 to the resulting number and interpret the result as a binary representation of the magnitude and add a negative sign (since the number begins...
Array slicing in Ruby: explanation for illogical behaviour (taken from Rubykoans.com)
I was going through the exercises in Ruby Koans and I was struck by the following Ruby quirk that I found really unexplainable:
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Fast Bitmap Blur For Android SDK
Currently in an Android application that I'm developing I'm looping through the pixels of an image to blur it. This takes about 30 seconds on a 640x480 image.
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How can building a heap be O(n) time complexity?
...?
Often, answers to these questions focus on the difference between siftUp and siftDown. Making the correct choice between siftUp and siftDown is critical to get O(n) performance for buildHeap, but does nothing to help one understand the difference between buildHeap and heapSort in general. Indeed, ...
How do I find the duplicates in a list and create another list with them?
How can I find the duplicates in a Python list and create another list of the duplicates? The list only contains integers.
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What does the [Flags] Enum Attribute mean in C#?
...t expect in bitwise operations, because by default the values start with 0 and increment.
Incorrect declaration:
[Flags]
public enum MyColors
{
Yellow, // 0
Green, // 1
Red, // 2
Blue // 3
}
The values, if declared this way, will be Yellow = 0, Green = 1, Red = 2, Blu...
How to implement a queue using two stacks?
Suppose we have two stacks and no other temporary variable.
20 Answers
20
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How to know if two arrays have the same values
...have these two arrays: one is filled with information from an ajax request and another stores the buttons the user clicks on. I use this code (I filled with sample numbers):
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How to scale down a range of numbers with a known min and max value
So I am trying to figure out how to take a range of numbers and scale the values down to fit a range. The reason for wanting to do this is that I am trying to draw ellipses in a java swing jpanel. I want the height and width of each ellipse to be in a range of say 1-30. I have methods that find t...
What's the difference between lapply and do.call?
I'm learning R recently and confused by two function: lapply and do.call . It seems that they're just similar to map function in Lisp. But why are there two functions with such a different name? Why doesn't R just use a function called map ?
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