Finding the second smallest integer in array

Question

We are required in our assignment to find the second smallest integer in one array recursively. However, for the sake of understanding the subject more, I want to do it iter

Answer 1

Here's a Swift version that runs in linear time. Basically, find the smallest number. Then assign the 2nd minimum number as the largest value. Then loop through through the array and find a number greater than the smallest one but also smaller than the 2nd smallest found so far.

func findSecondMinimumElementLinear(in nums: [Int]) -> Int? {
    // If the size is less than 2, then returl nil.
    guard nums.count > 1 else { return nil }

    // First, convert it into a set to reduce duplicates.
    let uniqueNums = Array(Set(nums))

    // There is no point in sorting if all the elements were the same since it will only leave 1 element
    // after the set removed duplicates.
    if uniqueNums.count == 1 { return nil }

    let min: Int = uniqueNums.min() ?? 0 // O(n)
    var secondMinNum: Int = uniqueNums.max() ?? 0 // O(n)
    // O(n)
    for num in uniqueNums {
        if num > min && num < secondMinNum {
            secondMinNum = num
        }
    }

    return secondMinNum
}