It is dynamic programming. Search in topcoder algo tutorials On Dec 16, 2011 10:33 AM, "Sangeeta" <[email protected]> wrote: > > Problem Statement > A sequence of numbers is called a zig-zag sequence if the differences > between successive numbers strictly alternate between positive and > negative. The first difference (if one exists) may be either positive > or negative. A sequence with fewer than two elements is trivially a > zig-zag sequence. > > For example, 1,7,4,9,2,5 is a zig-zag sequence because the differences > (6,-3,5,-7,3) are alternately positive and negative. In contrast, > 1,4,7,2,5 and 1,7,4,5,5 are not zig-zag sequences, the first because > its first two differences are positive and the second because its last > difference is zero. > > Given a sequence of integers, sequence, return the length of the > longest subsequence of sequence that is a zig-zag sequence. A > subsequence is obtained by deleting some number of elements (possibly > zero) from the original sequence, leaving the remaining elements in > their original order > > -- > You received this message because you are subscribed to the Google Groups "Algorithm Geeks" group. > To post to this group, send email to [email protected]. > To unsubscribe from this group, send email to [email protected]. > For more options, visit this group at http://groups.google.com/group/algogeeks?hl=en. >
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