Fast Bit Duplication

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Points: 10
Time limit: 2.5s
Memory limit: 64M

Problem type
Allowed languages
C, C++, Clang, Clang++

Given 32-bit unsigned integers, duplicate each bit in-place in the integer.

For example:

  • 10001_2 becomes 1100000011_2
  • 11110_2 becomes 1111111100_2


One function:

unsigned long long duplicatebits(unsigned long long);

Note: The function parameter is an unsigned long long instead of an unsigned int to remove the step of upcasting.

Your function may be called up to 10^8 times.


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