Learn to Program with C_ Learn to Program using the Popular C Programming Language ( PDFDrive )

Chapter 8 ■ Arrays
• The first time, we compare num[1] with num[0]; since num[1], 72, is larger
than num[0], 25, we update big to 1. This means that the largest number so
far is in position 1.
• Next, we compare num[2], 17, with num[big] (that is, num[1]), 72; since
num[2] is smaller than num[1], we go on to the next number, leaving big at 1.
• Next, we compare num[3], 43, with num[big] (that is, num[1]), 72; since
num[3] is smaller than num[1], we go on to the next number, leaving big at 1.
• Next, we compare num[4], 84, with num[big] (that is, num[1]), 72; since
num[4] is larger than num[1], we update big to 4. This means that the largest
number so far is in position 4.
• Next, we compare num[5], 14, with num[big] (that is, num[4]), 84; since
num[5] is smaller than num[4], we go on to the next number, leaving big at 4.
• Next, we compare num[6], 61, with num[big] (that is, num[4]), 84; since
num[6] is smaller than num[4], we go on to the next number, leaving big at 4.
• Since there is no next number, the process ends with the value of big being
4, the position of the largest number. The actual number is denoted by
num[big]; since big is 4, this is num[4], which is 84.
We can express the process just described by the following pseudocode:
big = 0
for h = 1 to 6
if num[h] > num[big] then big = h
endfor
print "Largest is ", num[big], " in position ", big
We will now write a function, getLargest, to find the largest value in an array. To be general,
we will specify which portion of the array to search for the value. This is important since, most
times, we declare an array to be of some maximum size (100, say) but do not always put 100
values in the array.
When we declare the array to be of size 100, we are catering for 100 values. But, at any time,
the array may have less than this amount. We use another variable (n, say) to tell us how many
values are currently stored in the array. For example, if n is 36, it means that values are stored in
elements 0 to 35 of the array.
So when we are finding the largest, we must specify which elements of the array to search. We
will write the function such that it takes three arguments – the array num, and two integers lo and
hi—and returns the position of the largest number from num[lo] to num[hi], inclusive. It is up
to the caller to ensure that lo and hi are within the range of subscripts declared for the array. For
instance, the call
• getLargest(score, 0, 6) will return the position of the largest number
from score[0] to score[6]; and the call
• getLargest(mark, 10, 20) will return the position of the largest number
from mark[10] to mark[20].
234
www.it-ebooks.info