Thread: Discrete Structures Class

Write an algorithm that returns the index of the last occurrence of the value key in a sequence s1, …,sn. If key is not in the sequence, the algorithm returns 0. Example, if the sequence is 12 11 12 23 and key is 12, the algorithm returns 3.

I need full explanation because I am not understanding this class just yet.

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Originally Posted by rharvell

Write an algorithm that returns the index of the last occurrence of the value key

That means start at the end, or the last element, and work toward the front looking for the requested value. For example, in 12 11 12 23, it means start at 23, is 23 the key (12), no, keep looking. Move back to 12. Is 12 the key (12), yes. Return it. Note that it is in index 2 not index 0. Also beware that this is to return the key, not the positional index, and 0 represents "not found"

Originally Posted by rharvell

in a sequence s1, …,sn.

This just means the set of elements can be any given length.

Originally Posted by rharvell

If key is not in the sequence, the algorithm returns 0.

If the requested key (12 in the example) is not found, return 0.