FoundationNumeric answer
Finding the unpaired ids · Part 1 of 3
An array holds integer order ids. Unless a part says otherwise, every id appears exactly twice except the ones you are asked to find, and you may use only extra memory.
The array is 4, 7, 2, 7, 4, 9, 2, and exactly one id appears once. XOR all the entries together. What do you get?
Answer with a number. Fractions, powers and expressions like 23/6 or C(52,5) are read correctly in practice.
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