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by adr
6494 days ago
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Suppose x = 0 and your list is [1,2,3,2,1]. If you xor 'x' with every number in your list then x = 1^2^3^2^1, which is the same as x = (1^1)^(2^2)^3 = 0^0^3 = 3. So, x=3 is the number that wasn't repeated. This works because a^b = b^a and a^a = 0. |
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