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Pseudocode help


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#1 puppet_master

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Posted 06 January 2013 - 18:05

Hi guys just wanted some help with Pseudocode. I just can get my head around it all I dont know why but I am really struggling. I have been asked to do the following. A program is needed that can accept 10 numbers as input from the user. The program should output the following information:

The sum of the numbers,
The mean of the numbers,
The median value for the numbers

any pointers

thanks


#2 fhpuqrgrpgvirzhpujbj

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Posted 06 January 2013 - 18:25

Don't know what language you're using so I can't make it particularly specific:

int sum = 0;
int mean = 0;
int median = 0;
int num4 = 0;
int num5 = 0;
for count = 0 to 10 { // For all ten of the user's numbers
  int num = get_number_from_user();
  sum = sum + num;
  if (count == 4) num4 = num; // If this is one of the two middle numbers, store it for calculating the median
  if (count == 5) num5 = num;
}
mean = sum / 10;
// EDIT: See discussion below about calculating the median if the numbers aren't entered in order
//median = (num4 + num5) / 2; // Two middle numbers so the median is their average
print(sum + " " + mean + " " + median);


#3 Phouchg

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Posted 06 January 2013 - 18:32

Posted Image


On a more serious note, it looks like you want your homework problem solved. Rather than handing it on a silver plate, would you mind showing us how far you've got already?

Edit: ok, let's hand it on a silver plate, because life's unfair. I'm out of here.

#4 Hardcore Til I Die

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Posted 06 January 2013 - 18:34

Don't know what language you're using so I can't make it particularly specific:

int sum = 0;
int mean = 0;
int median = 0;
int num4 = 0;
int num5 = 0;
for count = 0 to 10 { // For all ten of the user's numbers
  int num = get_number_from_user();
  sum = sum + num;
  if (count == 4) num4 = num; // If this is one of the two middle numbers, store it for calculating the median
  if (count == 5) num5 = num;
}
mean = sum / 10;
median = (num4 + num5) / 2; // Two middle numbers so the median is their average
print(sum + " " + mean + " " + median);


You are making the assumption that the user will input numbers in ascending numerical order.

I would suggest it needs to sort the numbers into ascending numerical order before trying to calculate the median.

Something like:

int sum = 0;
int mean = 0;
int median = 0;
int count = 10;
int num[] = {0};

for int N = 1 to count {
  num[N] = get_number_from_user();
  sum += num[N];
}
mean = sum / count;
sort(num[]);
median = (num[5] + num[6]) / 2;
print(sum + " " + mean + " " + median);


#5 fhpuqrgrpgvirzhpujbj

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Posted 06 January 2013 - 18:35

On a more serious note, it looks like you want your homework problem solved. Rather than handing it on a silver plate, would you mind showing us how far you've got already?


He asked for pseudocode instead of a solution which is certainly better than the average homework question around here. You still have to know what you're doing to a reasonable degree to get anything working from it.

You are making the assumption that the user will input numbers in ascending numerical order.
...
I would suggest it needs to sort the numbers into ascending numerical order before trying to calculate the median.


True, not sure why I was assuming they were sorted. Thanks for pointing that out.

#6 OP puppet_master

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Posted 07 January 2013 - 17:18

Im not asking for my homework to be done but a few pointers as I have been told that writing in pseudocode is the step in between the flow chart and the programming code, So when a programmer can look at this and they can make determine what I want.

The code I'm going to be using is VB.

This is what I have done so far.

BEGIN

PROMPT “Enter Numbers”

ADD and STORE Numbers = SUM

ARRANGE Numbers in Ascending order

Calculate MEAN of Numbers and STORE = SUM / 10

Calculate the MEDIAN and store = Number 5 + Number 6 / 2

PRINT SUM
PRINT MEAN
PRINT MEDIAN

END

Can you tell me what you think.

thanks

#7 Phouchg

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Posted 07 January 2013 - 20:31

Then please accept my apologies.

Yes, that's more like pseudocode - unrelated to any language in particular, understandable even to a non-programmer.
In classes we quickly went to Pascal syntax to get closer to the code, but flowcharts seem so much easier to do if one stays with informal syntax such as this.

Some comments:
* Even when using informal syntax, division takes precedence over addition. So the Number 5 + Number 6 / 2 line is confusing, and might creep an error in code later, if one is not careful. Either use parenthesis outright or just write the definition of median - mean of the two middlemost numbers.

* Regardless of syntax, SORT would be probably be better term instead of ARRANGE. Using engineering terms still helps if you later have to elaborate on how exactly one does that (all algorithms "sort")

#8 OP puppet_master

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Posted 07 January 2013 - 22:04

so i could write it like this...

Calculate the MEDIAN and store = ((Number 5 + Number 6 ) / 2)

#9 Phouchg

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Posted 08 January 2013 - 04:19

Looks good now (Y)


#10 Hardcore Til I Die

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Posted 08 January 2013 - 20:23

so i could write it like this...

Calculate the MEDIAN and store = ((Number 5 + Number 6 ) / 2)


That's fine but the outer brackets are redundant. Wrapping the entire equation in brackets is the same as having none, so ((Number 5 + Number 6) / 2) is the same as (Number 5 + Number 6) / 2.

#11 threetonesun

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Posted 08 January 2013 - 20:44

FWIW, 5 + 6 is relative to the starting number. If you were just shoving the input into an array, it would be 0 - 9, and the median would be (4+5)/2. Unless specified, I would assume any pseudocode to count from zero.

#12 Hardcore Til I Die

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Posted 08 January 2013 - 20:50

FWIW, 5 + 6 is relative to the starting number. If you were just shoving the input into an array, it would be 0 - 9, and the median would be (4+5)/2. Unless specified, I would assume any pseudocode to count from zero.


Not sure if I'm misunderstanding what you're saying or if I'm just confused by your explanation, but the median is worked out as follows:-

1. Sort the numbers into ascending order.
2. If the number of numbers is odd, the median is the middle number.
3. If the number of numbers is even, the median is the mean of the middle two numbers.

Example 1:

1, 2, 3, 10, 11 - the median is 3 because it's the middle number.

Example 2:

1, 2, 3, 4, 10, 11 - median is 3.5, because you take the middle two numbers and work out the mean. (3 + 4) / 2 = 3.5.

#13 Phouchg

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Posted 08 January 2013 - 21:27

Must have meant array indexing - zero-based or one-based. Zero-based being very prevalent, but nevertheless not universal. We must not make assumptions - the very idea of pseudocode (of informal syntax) is meant to be readable (so one-based would be more natural) and easy to translate among different languages (even though *we* know that VB, zero-based, will be used).

If anything, writing only the definition of median would be the most acceptable.

#14 Hardcore Til I Die

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Posted 08 January 2013 - 22:26

Must have meant array indexing - zero-based or one-based. Zero-based being very prevalent, but nevertheless not universal. We must not make assumptions - the very idea of pseudocode (of informal syntax) is meant to be readable (so one-based would be more natural) and easy to translate among different languages (even though *we* know that VB, zero-based, will be used).

If anything, writing only the definition of median would be the most acceptable.


Just reread his post and I agree he was probably talking about array indexing.

Pseudo code being language independent and supposed to be readable, I thought it would make more sense to use a one-based array. Clearly when translating it into actual code the user must make the necessary adjustments if it is a zero-based language.

#15 threetonesun

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Posted 09 January 2013 - 01:08

Must have meant array indexing - zero-based or one-based. Zero-based being very prevalent, but nevertheless not universal. We must not make assumptions - the very idea of pseudocode (of informal syntax) is meant to be readable (so one-based would be more natural) and easy to translate among different languages (even though *we* know that VB, zero-based, will be used).

If anything, writing only the definition of median would be the most acceptable.


Well, you know that 10 is going to be the number of inputs as well.

You could say MEDIAN = LENGTH OF ARRAY MODULO 2 ? ROUND UP ARRAY[LENGTH/2] : (ARRAY[LENGTH/2] + ARRAY[LENGTH/2 + 1]) / 2

Thereby negating the need to know the index or the number of inputs and defining median.