Different counting for arrays

Question

If i have 2 parallel arrays. One is is short[] and other String[]. short has a range of marks. short[95, 96, 95, 99, 100]. String has names of students [Mark, Steve, Emma, Rachael, Justin] They have already been declared and are corresponding. I know how to sort alphabetically and according marks. The question asks me to print out " * " for the times a student has received a grade. The user does not put any input in. for example: This would be the output.

100 = * (As only 1 person got a 100)
99 = *
96 = *
95 = **

I have to get to that output without any user inputs. I kinda think i have an idea of how to do it but im pretty lost. I dont even know how to start. All i know is a counter has to be used but that would only work if a user inputs a mark. I dont know how to do it without any input.

Do you want to generate a [histogram](http://en.wikipedia.org/wiki/Histogram)? — Kninnug, Apr 15 '13 at 15:57

score 0 · Accepted Answer · answered Apr 15 '13 at 16:00

0

assuming - no of students = no

and your 2 arrays are

String [] students;

and

short [] marks.

Create a third array

int [] count = new int[101];


int i = 0;

for(i = 0; i < no; ++i)
    ++count[marks[i]];

count array will contain no of times each mark occurs i.e. count[50] will contain no of students who got 50.

You can print it out as

for(int i = 0; i < no; ++i)
    System.out.println(i + " = " + count[i]);

answered Apr 15 '13 at 16:00

user93353

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Is the first loop really necessary? I thought Java initialized the `int`s to zero automagically. – Kninnug Apr 15 '13 at 16:01
i understand that, what is the [101] for? – user2278109 Apr 15 '13 at 16:02
@Kninnug habit from c++, updated. – user93353 Apr 15 '13 at 16:03
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@user2278109 there are 101 possible marks a user can get 0, 1, 2 --- 100. Try out the code and see. – user93353 Apr 15 '13 at 16:03
oh rite i get it! thanks, only new to java so still a bit confused about everything – user2278109 Apr 15 '13 at 16:06
@user93353 It's a good habit though ;) – Kninnug Apr 15 '13 at 16:06
it says cannot convert from int to String? is there a way around this? @user93353 – user2278109 Apr 15 '13 at 16:18
@user2278109 - what line gives that error? – user93353 Apr 15 '13 at 16:18
++count[marks[i]]; @user93353 – user2278109 Apr 15 '13 at 16:19
What have you declared `count` as. And what have you declared `marks` as? – user93353 Apr 15 '13 at 16:21
count is String as using a method and passing down the String[]users array – user2278109 Apr 15 '13 at 16:23
I have declared count in my answer - it has to be an array of ints - `int [] count = new int[101];` – user93353 Apr 15 '13 at 16:24
okay thanks, i'll play around with it and figure it out! @user93353 thanks for your help – user2278109 Apr 15 '13 at 16:25

score 0 · Answer 2 · answered Apr 15 '13 at 16:01

0

Use an array, such that the 100th index corresponds to the grade 100, the 99th index corresponds to the grade 99, etc. This way if somebody gets a grade g you can just increment the gth element of the array.

answered Apr 15 '13 at 16:01

Zim-Zam O'Pootertoot

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Different counting for arrays

2 Answers2