Find first and last set bit of a long integer: Difference between revisions
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Define routines (or operators) '''lwb''' and '''upb''' that find the ''first'' and ''last'' set bit in a binary value. Implement using a binary search to find the location of the particular upper/lower bit. |
Define routines (or operators) '''lwb''' and '''upb''' that find the ''first'' and ''last'' set bit in a binary value. Implement using a binary search to find the location of the particular upper/lower bit. |
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Also: Define the reverse routines (or operators) '''rlwb''' and '''rupb''' that find host's ''integers'' least- and most-significant set bit in a binary value expressed in [[wp:Bit_numbering#LSB_0_bit_numbering|LSB 0 bit numbering]], i.e. indexed from the extreme right bit. |
Also: Define the reverse routines (or operators) '''rlwb''' and '''rupb''' that find host's ''positive integers'' least- and most-significant set bit in a binary value expressed in [[wp:Bit_numbering#LSB_0_bit_numbering|LSB 0 bit numbering]], i.e. indexed from the extreme right bit. |
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Use primarily '''bit''' operations, such as '''and''', '''or''', and bit shifting. Avoid additions, multiplications and especially avoid divisions. |
Use primarily '''bit''' operations, such as '''and''', '''or''', and bit shifting. Avoid additions, multiplications and especially avoid divisions. |
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