Mode
PROBLEM
The problem is to determine the most frequently occuring value, called the mode, of a sorted array.
ALGORITHM
The elegant algorithm used to compute the mode was invented by Griffits.
IMPLEMENTATION
Unit: internal function
Global variables: the input sorted array A. of arbitrary elements
Parameter: a positive integers N  number of elements in A.
Returns: Couple of values Mode and Frequence of mode separated by blanks.
MODE: procedure expose A.
parse arg N
Mode = A.1; Frequence = 1
do J = 2 to N
JmFrequence = J  Frequence
if A.J = A.JmFrequence
then do
Frequence = Frequence + 1; Mode = A.J
end
end
return Mode Frequence

EXAMPLE
N = 5
A.1 = 1; A.2 = 2; A.3 = 2; A.4 = 3; A.5 = 5
say MODE(N)
exit
MODE: procedure expose A.
...

displays 2 2
Literature
Gehani N., Ada  An Advanced Introduction PrenticeHall, Inc. Englewood Cliffs, New Jersey 1983
