Find Largest & Second Largest Number Index in Array - Ask Algorithm

[nenyan]

a function: can give the index of the largest number in an array. also give the index of the second largest number, and the index of the third and the forth.


such as

a={1,2,3,5,7,99,121,3,2,24,10}
the code can give the result followed:
6，5，9，10

how to make the function?

 

[nenyan]

eh, I got one

max[4]=-100;
maxIndex[4]=-1;
for i=1:4
for j=a1:an
if aj>maxi
max=aj;
maxindex=j;
end if
end for j
end for i

 

[chiro]

One way would be to use any sort algorithm, but instead of outputting the values to a target array, you give your sort function an array that is the same dimension but contains index information.

So basically you initialize your index array to a = i and then in your sort function swap the values in your index array instead of modifying your values in the actual data array itself.

You can use the above idea with any sort implementation.

 

[nenyan]

That's a good idea! Thank you.

One way would be to use any sort algorithm, but instead of outputting the values to a target array, you give your sort function an array that is the same dimension but contains index information.

So basically you initialize your index array to a = i and then in your sort function swap the values in your index array instead of modifying your values in the actual data array itself.

You can use the above idea with any sort implementation.

 

[LudusRex]

To create a function that can give the index of the largest and second largest numbers in an array, we can use a sorting algorithm to sort the array in descending order. Once the array is sorted, the first element will be the largest number and the second element will be the second largest number. We can then return the indices of these two elements.

To also find the indices of the third and fourth largest numbers, we can continue the sorting algorithm and return the indices of the third and fourth elements in the sorted array.

Alternatively, we can use a loop to iterate through the array and keep track of the largest and second largest numbers and their respective indices as we go. This would require comparing each element to the current largest and second largest numbers and updating them accordingly. Once the loop is finished, we can return the indices of these numbers.

In both cases, it is important to consider edge cases, such as if the array is empty or if there are duplicate numbers in the array. Overall, the function should be designed to handle any type of array and provide accurate indices for the largest and second largest numbers.