Update viterbi.nim

Adding description and reference to the Viterbi Algorithm

Author: SatinWukerORIG

dynamic_programming/viterbi.nim

@@ -1,4 +1,14 @@
 # Viterbi
+## The Viterbi algorithm is a dynamic programming algorithm
+## for obtaining the maximum a posteriori probability estimate
+## of the most likely sequence of hidden states
+## https://en.wikipedia.org/wiki/Viterbi_algorithm
+##
+## Time Complexity: O(K2n)
+## Space Complexity: O(Kn)
+## https://www.cs.cmu.edu/~epxing/Class/10708-20/scribe/lec4_scribe.pdf
+
+
 {.push raises: [].}
 
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