How to find unique words given a list of words in R

Question

I have a list of words

a = c("when","to","use","each","effect","","recognizing","each","effect","?",":")
a
[1] "when"        "to"          "use"         "each"       
[5] "effect"      ""            "recognizing" "each"       
[9] "effect"      "?"           ":" 

This list could have contained thousands of words. How can I effectively find out the unique words, i.e. "when" "to" "use" "each" "effect" "recognizing"?

I am trying to avoid for loops whenever possible.

Thanks

Answer 1

unique(a)

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table(a)

Answer 2

You can use a hashmap to maintain the list instead of using an array. It would automatically maintain the uniqueness of your data.