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POBest algorithm for delete duplicates in array of strings
 

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  1. POBest algorithm for delete duplicates in array of strings
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    <p>Today at school the teacher asked us to implement a duplicate-deletion algorithm. It's not that difficult, and everyone came up with the following solution (pseudocode):</p> <pre><code>for i from 1 to n - 1 for j from i + 1 to n if v[i] == v[j] then remove(v, v[j]) // remove(from, what) next j next i </code></pre> <p>The computational complexity for this algo is <code>n(n-1)/2</code>. (We're in high school, and we haven't talked about big-O, but it seems to be <code>O(n^2)</code>). This solution appears ugly and, of course, slow, so I tried to code something faster:</p> <pre><code>procedure binarySearch(vector, element, *position) // this procedure searches for element in vector, returning // true if found, false otherwise. *position will contain the // element's place (where it is or where it should be) end procedure ---- // same type as v vS = new array[n] for i from 1 to n - 1 if binarySearch(vS, v[i], &amp;p) = true then remove(v, v[i]) else add(vS, v[i], p) // adds v[i] in position p of array vS end if next i </code></pre> <p>This way <code>vS</code> will contain all the elements we've already passed. If element <code>v[i]</code> is in this array, then it is a duplicate and is removed. The computational complexity for the binary search is <code>log(n)</code> and for the main loop (second snippet) is <code>n</code>. Therefore the whole CC is <code>n*log(n)</code> if I'm not mistaken.</p> <p>Then I had another idea about using a binary tree, but I can't put it down.<br> Basically my questions are:</p> <ul> <li> Is my CC calculation right? (and, if not, why?)</li> <li> Is there a faster method for this?</li> </ul> <p>Thanks</p>
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    1. COJust for the record, this is indeed O(n^2).
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    2. COWhat is the type of `vS`, and what does `add` do exactly?
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    3. CO@Robin Green: vS is like v, and add adds the specified element in the specified position
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