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I was going though this blog and it says

You can represent a list of distinct integers no larger than N using exactly N bits: if the integer i appears in your list, you set the i th bit to true. Bits for which there is no corresponding integers are set to false. For example, the integers 3, 4, 7 can be represented as 00011001. As another example, the integers 1, 2, 7 can be represented as 01100001.

Can someone please explain me how [3, 4, 7] = 00011001 and [1, 2, 7] = 01100001 and also why 8 bits are taken?

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Think of it as ['0d: OFF', '1st: OFF', '2nd: OFF', '3rd: ON', '4th: ON', '5th: OFF', '6th: OFF', '7th: ON'].

  • Hence the 00011001. – 94239 Dec 10 '13 at 12:35
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    ohh starting with 0 and counting left to right. Tx a lot! – Aniket Thakur Dec 10 '13 at 12:36
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    @AniketThakur: as N = 7 you only need 7 bits, the first zero moght be left padding to store it into a byte (8 bits). – Marjan Venema Dec 10 '13 at 14:38

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