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contest_2011-09-13 [2011/09/08 17:10]
jtkorb created
contest_2011-09-13 [2011/09/20 14:34] (current)
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   * A: [[http://​uva.onlinejudge.org/​index.php?​option=com_onlinejudge&​Itemid=8&​category=33&​page=show_problem&​problem=1143|Pairsumonious Numbers]]   * A: [[http://​uva.onlinejudge.org/​index.php?​option=com_onlinejudge&​Itemid=8&​category=33&​page=show_problem&​problem=1143|Pairsumonious Numbers]]
 +  * B: [[http://​uva.onlinejudge.org/​index.php?​option=com_onlinejudge&​Itemid=8&​category=32&​page=show_problem&​problem=1132|Longest Nap]]
 +  * C: [[http://​uva.onlinejudge.org/​index.php?​option=com_onlinejudge&​Itemid=8&​category=32&​page=show_problem&​problem=967|Shoemaker'​s Problem]]
 +  * D: [[http://​uva.onlinejudge.org/​index.php?​option=com_onlinejudge&​Itemid=8&​category=34&​page=show_problem&​problem=1154|How Many Pieces of Land?]]
 +  * E: [[http://​uva.onlinejudge.org/​index.php?​option=com_onlinejudge&​Itemid=8&​category=34&​page=show_problem&​problem=990|Self-describing Sequence]]
  
-If you've already solved one or more of these problems, try (1) solving again without referring to your old solution, and/or (2) using a different language (Java or C++).  If you want to work on an additional problem from this chapter, let [[jtk@purdue.edu|me]] know.+//​Remember:// ​If you've already solved one or more of these problems, try (1) solving again without referring to your old solution, and/or (2) using a different language (Java or C++).  If you want to work on an additional problem from the book, let [[jtk@purdue.edu|me]] know.
  
 **Hints:** **Hints:**
  
-  * A: For Pairsumonious Numbers, you'll need to store the N*(N-1)/2 values into a sorted array to use them to compute ​the sums.  This problem ​gets you set up for that+  * A: Solve [[prelude_to_pairsumonious_numbers|Prelude to Pairsumonious Numbers]] first. ​ An exhaustive search of all possible sums works. ​ Create a candidate vector by seeding ​the first location with 1/2 of the first (lowest) sum.  Extend the vector by subtracting the current vector element from one of the sums.  Each time the vector fills, check to see if it is a solution. ​ If not, backtrack by selecting a different sum value at each of the extension steps. ​ Tricky bits: watch for sums less than 0 and only extend the current candidate solution vector if the entries are non-decreasing.  ​The check solution procedure verifies that the pair-wise sum of every pair of values has been found. 
 +  * B: This problem ​is from the chapter on sorting. ​ Comparators help here. 
 +  * C: See B. 
 +  * D: Once you see the trick, the solution is easy with big integers (are they required?)
 +  * E: Pre-compute a run-length encoded array to represent f, then do a binary search to find f(n).
contest_2011-09-13.1315527032.txt.gz · Last modified: 2011/09/08 17:10 by jtkorb