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    <p>You are right that recursion is the way to go. The example you worked thru w/ the little bit of math was all correct, but kind of indirect.</p> <p>Here's some pseudocode:</p> <pre><code> def permute(charSet, soFar): if charSet is empty: print soFar //base case for each element 'e' of charSet: permute(charSet without e, soFar + e) //recurse </code></pre> <p>example of partial recursion tree</p> <pre><code> permute({A,B,C}, '') / | \ permute({B,C}, 'A') permute({A,C}, 'B') permute({A,B}, 'C') / \ permute({A}, 'BC') permute({C}, 'BA') | permute({}, 'BCA')&lt;---BASE CASE, print 'BCA' </code></pre> <hr> <h2>EDIT</h2> <p>To handle repeated characters without duplicating any permutations. Let <code>unique</code> be a function to remove any repeated elements from a collection (or string that is being treated like an ordered character collection thru indexing).</p> <p>1) Store results (including dupes), filter them out afterwards</p> <pre><code> def permuteRec(charSet, soFar): if charSet is empty: tempResults.add(soFar) //base case for each element 'e' of charSet: permute(charSet without e, soFar + e) //recurse global tempResults[] def permute(inString): permuteRec(inString, '') return unique(tempResults) print permute(inString) </code></pre> <p>2) Avoid generating duplicates in the first place</p> <pre><code> def permute(charSet, soFar): if charSet is empty: print soFar //base case for each element 'e' of unique(charSet): permute(charSet without e, soFar + e) //recurse </code></pre>
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    1. USTom Zych
    1. USjon_darkstar
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    1. COCan you explain a bit further cause i didn't fully understand it so the base case will be an empty string? my idea of the base case was both empty and just 1 character of a string.
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      1. USJohn Smith
    2. COMy Base case: if length of string is less than 2 print 0 for an empty string, Same string for a 1 character string.
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    3. COon the first call `charSet` will be collection containing all n elements and `soFar` will be empty. on base cases `charSet` will be empty and `soFar` will contain all n elements. `soFar` must be ordered, `charSet` can be ordered or unordered
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