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A positive integer is given. How can you determine whether it is a
power of 2 without using recursion and floating point operations? 


Puzzle statistics "A power of 2".
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A text of a C code is given below. Find three different ways to
replace one symbol so that the resulting code would print 20
asterisks. A symbol has to be replaced, not added or deleted.
main() { int i, N=20; for (i = 0 ; i < N ; i) { printf("*"); } } 


Puzzle statistics "Twenty asterisks".
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I. A large array of integer values is given. All values appear twice
except one which appears once. How to find this value using at most
O(1) additional variables and browsing through the entire array at
most O(1) times.
II. Same, except now exactly two values appear once. 


Puzzle statistics "An integer array".
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