How to summarize the elements of the list each with each?

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In the given list of integers, non-negative numbers, determine whether there are a pair of numbers in the list, so that their sum is equal to the specified number. If yes, return their indexes in the form of Pair from smaller to larger. If not, return Pair (-1, -1).

fun findSumOfTwo(list: List<Int>, number: Int): Pair<Int, Int> {
    for (item in list) {
        for (digit in list - 1) {
            if (item + digit == number) return Pair (list[item], list [digit])
        }
    }
    return Pair (-1, -1)
}

I know that besides the fact that my code does not work, it is far from perfect. And I would like to get the most idiomatic solution from the point of view of the Kotlin language.

This is literally one of the most common interview questions.

Your current solution is has a time complexity of O(N^2) which is not good, however, it has a space complexity of O(1), which is good.

Here is a working version of this approach:

fun findSumOfTwo(arr: IntArray, targetSum: Int): Pair<Int, Int> {
    if (arr.size < 2) return Pair(-1, -1)
    var sum: Int
    for (i in 0..arr.size - 2) {
        for (j in i + 1..arr.size - 1) {
            sum = arr[i] + arr[j]
            if (sum == targetSum)  {
                if (arr[i] < arr[j]) {
                    return Pair(i, j)
                }
                return Pair(j, i)
            }
        }
    }
    return Pair(-1, -1)
}

After coding something similar to above your interviewer will most likely ask you to optimize the time complexity to O(N), (space complexity will need to increase to O(N) but that is ok, time complexity is more important in most cases).

You can do that by using one pass using a HashMap:

fun findSumOfTwo(arr: IntArray, targetSum: Int): Pair<Int, Int> {
    if (arr.size < 2) return Pair(-1, -1)
    var map = HashMap<Int, Int>()
    for (i in 0..arr.size - 1) {
        var complement = targetSum - arr[i]
        if (map.containsKey(complement)) {
            var complementIndex = map.get(complement)!!
            if (arr[i] < complement) {
                return Pair(i, complementIndex)
            }
            return Pair(complementIndex, i)
        }
        map.put(arr[i], i)
    }
    return Pair(-1, -1)
}

Note: That the above two solutions make two assumptions: 1) The input array is not sorted. 2) If there is more than one valid pair in the input array returning only one valid pair is ok.

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Since you only care for one pair of indices which element's sum equals a certain number, use forEachIndexed:

fun findSumOfTwo(list: List<Int>, number: Int): Pair<Int, Int> {

   list.forEachIndexed { i1, e1 ->
        list.forEachIndexed { i2, e2 ->
            if(e1 + e2 == number) {
                return i1 to i2
            }
        }
    }

    return Pair (-1, -1)
}

Data Analysis Using Stata, After summarizing the incomes of all educational groups of males, it does the Following that are elements you must type: the element name (Iname), the list  Initialise an empty list lst = []. Read each number using a for loop. In the for loop append each number to the list. Now we use predefined function sum () to find the sum of all the elements in a

(I just realize that this is NOT valid. So, plz skip this solution :( ) There are 2 comments here.

  1. Imagine if number = -2 and list = listOf(-1). Then Pair(-1, -1) cannot tell us whether this pair is available in out list. Another thing is that Kotlin comes null safety feature. We can return it as nullable type, in this case, Pair<Int, Int>?. If our function returns null value, it means that there are no possible pair that we are looking for explicitly.
  2. My alternative solution comes with concept of functional programming.
fun findSumOfTwo(list: List<Int>, number: Int): Pair<Int, Int>? {
    return list
            .flatMap { it1 -> list.map { it2 -> Pair(it1, it2) } }
            .firstOrNull { it.first + it.second == number }
}

Feel free to have discussion :)

Physician Documentation for Reimbursement, Discharge Summary DISCHARGE SUMMARY ELEMENTS (All elements are required.) COMMENT Admitting or provisional diagnosis Final diagnosis List first. Python Program to find Sum of Elements in a List. This python program allows user to enter the length of a List. Next, we used Python For Loop to add numbers to the list. TIP: Python sum function returns the sum of all the elements in a List.

The Elements of Style Summary: Writing Tips from the Most , In essence, the article represents an informal summary of The Elements of Style, This writing guide is composed of four sections, each of which contains tips that A notable exception to this rule is when you list several examples in a row,  C# Sum Method: Add up All Numbers. Use the Sum extension method and the selector overload. Include the System.Linq namespace. Sum. This method adds up all values in an IEnumerable. It computes the sum total of all the numbers in an array, or List, of integers. This extension method in LINQ provides an excellent way to do this with minimal calling code.

Federal Register, of each such constitutional issue which it proposes to raise; and (2) A summary of the the Statement must list each such document by title, summarize the relevant (TRU elements are elementS having atomic numbers greater than 92.)​  Suppose that you want to calculate the sum of a list of numbers such as: \([1, 3, 5, 7, 9]\). An iterative function that computes the sum is shown in ActiveCode 1. The function uses an accumulator variable (theSum) to compute a running total of all the numbers in the list by starting with \(0\) and adding each number in the list.

Guidelines for Writing a Summary, To include every detail is neither necessary nor desirable. Instead, you should extract only those elements that you think are most important—the main idea Review all the ideas on your list, and include in your summary all the ones that are  View Lab Report - summarize.py from CS 1026A at Western University. # # Assignment #2 # Output of list elements for testing program # # Function summarize simply outputs the lists for each shape with

Comments
  • if you don't want a java solution, please remove that tag
  • I put this one because many Java developers know Kotlin very well and can help
  • if they know Kotlin very well, they would be watching the Kotlin tag as well
  • Solution doesnt work with empty list.
  • @A.Rost what do you mean? If the list is empty, (-1, -1) will be returned.
  • assertEquals( Pair(-1, -1), findSumOfTwo(emptyList(), 1) ) This JUnit test is failed with actual result (2, 2) instead of (-1, -1)
  • @A.Rost this is impossible. if list is empty, the loop will never run... resulting in returning Pair(-1, -1). see for yourself: pl.kotl.in/rysVn2bmE
  • @A.Rost the result of findSumOfTwo(listOf(1, 2, 3), 6) is (2, 2) which is the index of 3, so it is correct if the same number can be referenced twice. If you don't want that the if expression should look like this if(e1 + e2 == number && i1 != i2), so no big change. see how short and concise it still is.
  • I'm sorry. I forgot to add in the condition that only positive numbers are in the list. Already edit the question.