Thread: Recursive algorithm

Give a recursive algorithm for finding the sum of the first n positive integer.

Procedure sum of integer ( n : positive integer )
if n<= 0
then sum of integer(n) := 0
else sum of integer(n) := n+ sum of integer(n)

is it correct or not ?? some one please help me ??

if n<= 0
then sum of integer(n) := 0
else sum of integer(n) := n+ sum of integer(n)

That should be
else sum of integer(n+1) = sum of integer(n) + 1

Originally Posted by bhuvan

Give a recursive algorithm for finding the sum of the first n positive integer.

Procedure sum of integer ( n : positive integer )
if n<= 0
then sum of integer(n) := 0
else sum of integer(n) := n+ sum of integer(n)

is it correct or not ?? some one please help me ??

You have to have express sum_of_integer(n) in terms of sum_of_integer(n-1) so:

Also as n is declared as a positive integer you cannot test if it is <=0

Code:

Procedure sum_of_integer ( n : positive integer )
  if n== 1
    then
       sum_of_integer := 1
    else
       sum_of_integer := 1+ sum_of_integer(n-1)

CB

Thank you very much for your reply but i do not understand the logic

Procedure sum_of_integer ( n : positive integer )
if n== 1
then
sum_of_integer(n) := 1
else
sum_of_integer(n) := 1+ sum_of_integer(n-1)
what is the value of sum_of_integer(n-1) ?? if we take n = 2 if you can describe little bit ?? appreciate your reply.

Thanks

Originally Posted by bhuvan

Thank you very much for your reply but i do not understand the logic

Procedure sum_of_integer ( n : positive integer )
if n== 1
then
sum_of_integer(n) := 1
else
sum_of_integer(n) := 1+ sum_of_integer(n-1)
what is the value of sum_of_integer(n-1) ?? if we take n = 2 if you can describe little bit ?? appreciate your reply.

Thanks

Well it is confusing as I retained your confusion of the name of the procedure (it should be a function by the way) and the name of the return value, try:

Code:

Function sum_of_integer ( n : positive integer )
  if n== 1
    then
        return 1
    else
        return 1+ sum_of_integer(n-1)

CB

Give a recursive algorithm for finding the maximum of the finite set of integer, making use of the fact that the maximum of n integer is the larger of the last integer in the list and the maximum of the first n-1 integer in the list.

procedure largest(a1,a2,.....,an: integer)
if n=1
then largest (a1,a2,.....,an: integer) : = a1
else largest(a1,a2,.....,an: integer) : = max(largest(a1,a2,.....,an-1),an)

is the answer correct or not ?? if not please suggest the correct answer. appreciate your reply.

Thanks

Originally Posted by bhuvan

Give a recursive algorithm for finding the maximum of the finite set of integer, making use of the fact that the maximum of n integer is the larger of the last integer in the list and the maximum of the first n-1 integer in the list.

procedure largest(a1,a2,.....,an: integer)
if n==1
then largest (a1,a2,.....,an: integer) : = a1
else largest(a1,a2,.....,an: integer) : = max(largest(a1,a2,.....,an-1),an)

is the answer correct or not ?? if not please suggest the correct answer. appreciate your reply.

Thanks

I think your pseudo-code use is not acceptable, something more like:

Code:

procedure largest(n:unsigned, a[1:n]: integer)
  if n=1
    then 
       return  a[1]
    else
       return  max(largest(n-1, a[1:n-1]),a[n])

would be better.

Alternativly can you give a link to a site that specified the syntax for your pseudo-code.

CB