I am doing the mooc(part 7/14, doing sorting algorithms) and i need help on index of smallest from

[tranquil inlet]

I am doing the mooc(part 7/14, doing sorting algorithms) and i am doing the sorting exercise. i am stuck on part 3. the part says that i have to make a method to find the index of the smallest number in an array, but with one of the parameters is a startingIndex, which the method is only going to find the smallest index of the array without the values of the indexes before the starting index. i cant figure out how to do it. i have tried making a new array, only adding values to it(from the array) when the index is bigger or equal to the starting Index and then returning the indexOfSmallest of that new array. I have also tried making an indexOf method and then finding the smallest of the numbers(after the starting index) in the array and then getting the index of that number, but that didnt work. My file is in the message. i have deleted my past attempts from the file(i still have them somewhere else tho). could someone help me?(sry if any part of this message didnt make sense)

[high steppe]

I uploaded your attachments as Gist.

<@&987246399047479336> please have a look, thanks.

[high steppe]

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[junior jolt]

would be helpful if you show us your own attempt and what you dont understand in that attempt on why its not working etc

also your indexOfSmallest works?

hm according to the code it shouldnt always work

if you got indexOfSmallest correct then you can simply use 90% of it in the indexOfSmallestFrom

[tranquil inlet]

i am going to have lunch and then i am going to see if indexOfSmallest 100% works.

i checked that indexOfSmallest and i cant find a case that it doesnt work, so here is my previous attemts at doing indexOfSmallestFrom

public static int indexOfSmallestFrom(int[] array, int startIndex) {
        // first attempt
        int[] newArray= new int[array.length-startIndex];
        for(int i = 0;i< array.length;i++){
            if(i>=startIndex){
                newArray[i-startIndex]=array[i];
                System.out.println(newArray[i-startIndex]);
            }
        }
        return indexOfSmallest(newArray);
        // second attempt
        int smallest = 0;
        for(int i = 0; i< array.length; i++ ){
            if(i<=startIndex){
                 smallest = array[i];
            }
        }

        return indexOf(array, smallest);
    }
    // method for second attempt
    public static int indexOf(int[] array, int value) {
        for(int i =0; i<array.length; i++){
            if(array[i]==value){
                return i;
            }
        }
        return -1;
    }

[junior jolt]

    public static int indexOfSmallest(int[] array){
        int index = array[0];
        for(int i = 0; i< array.length; i++ ){
            if(array[i]==smallest(array)){
                index=i;
            }
        }
        return index;
    }

there is already something wrong with this

imagine this array:

6, 12, 60, 64

what will it return

also the if check is just wrong

you always go run the smallest method for each time you are checking

the result of smallest(array) will never change

ok so lets continue how I would solve this problem after finishing the first part

you got this:

    public static int smallest(int[] array){
        int smallest= array[0];
        for(int small : array){
            if(smallest>small){
                smallest=small;
            }
        }
        return smallest;
    }

and then the question is to return the index instead of the actual number

so I would just add a variable to this which always stores the index of the smallest number

but therefore you need to use a fori loop instead

[tranquil inlet]

idk what fori loops are, they werent in the previous parts of the mooc

[junior jolt]

? just the normal for loop

for(int i = 0; i < array.length; i++) {

}

example for loop

[tranquil inlet]

oh ok

[junior jolt]

and these store the current index

which will be needed in order to store the index of the current smallest

[tranquil inlet]

do you mean like getting the index of smallest and the smallest in the same method?

[junior jolt]

its basically extending this method with an extra feature and putting it in a new method

[tranquil inlet]

oh ok i get it

[junior jolt]

so you want to return the index of the smallest

so you would need a variable which stores the index of the smallest

and that variable should change when you found a new smaller value in the array

and at the end return the index

[tranquil inlet]

so something like this?

public static int indexOfSmallest(int[] array){
        int smallest= array[0];
        int index = 0;
        for(int i = 0; i< array.length; i++ ){
            if(smallest>array[i]){
                smallest=array[i];
                index=i;
            }
        }
        return index;
    }

[junior jolt]

yeah

I would maybe change the if condition to this array[i] < smallest, makes it better readable imo

[tranquil inlet]

for me > and < had always been confusing, from the first time we learnt them at school, to now

[junior jolt]

xD

kinda simple though

x < y x smaller y

[tranquil inlet]

yeah ik, but like if someone made me look at a < or > operator, i would not be able to tell them which is smaller/bigger almost instantly. i would need to look at it carefully first

[junior jolt]

I kinda learned it like this
the area of the left is smaller
so the it shows that the left is smaller than the right

[tranquil inlet]

ok thank you

[junior jolt]

left is bigger than the right

ok so lets start with part 3

its basically part 2

but instead of checking the whole array you should start at a given point

[tranquil inlet]

i tried something while you where explaining

public static int indexOfSmallestFrom(int[] array, int startIndex) {
        int smallest= array[0];
        int index = 0;
        for(int i = 0; i< array.length; i++ ){
            if(smallest>array[i]){
                if(i>=startIndex){
                    smallest=array[i];
                    index=i;
                }
            }
        }
        return index;
    }

[junior jolt]

public static int indexOfSmallest(int[] array){
        int smallest= array[0];
        int index = 0;
        for(int i = 0; i< array.length; i++ ){
            if(smallest>array[i]){
                smallest=array[i];
                index=i;
            }
        }
        return index;
    }

so if we are taking this from part 2, we iterate through the whole array from index 0 -> array.length
but now in part 3 we should only check numbers from index startIndex -> array.length

so what would you need to change

its just one small change

[junior jolt]

this might work but there is a better solution

because now you are iterating again through the whole array 0 -> array.length but
the first array entries from 0 -> startIndex - 1 are not needed

[tranquil inlet]

ok i tried once again

int smallest= array[startIndex];
        int index = startIndex;
        for(int i = startIndex; i< array.length; i++ ){
            if(smallest>array[i]){
                smallest=array[i];
                index=i;
            }
        }
        return index;

[junior jolt]

yeah exactly

though

yeah nvm

all good

[tranquil inlet]

Ok thank you so much SquidXTV!!!! now my program works( and I know how to recognize which is smaller and bigger in > and < quickly!)