ListDiff.swift

class ListDiff<T : Hashable> {
    typealias IndexList = [Int]
    typealias FromIndexToIndexList = [(from: Int, to: Int)]

    // A list of indexes of where items were added.
    let added: IndexList
    // A list of indexes where items that have disappeared used to be.
    let deleted: IndexList
    // A list of tuples of indexes representing the old and new indexes of items that moved.
    let moved: FromIndexToIndexList

    init(before: [T], after: [T]) {
        // Create a map with all the items in the smaller list mapped to indexes.
        let beforeIsSmaller = before.count < after.count
        var map = [T: Int]()
        for (index, item) in enumerate(beforeIsSmaller ? before : after) {
            map[item] = index
        }

        var added = IndexList()
        var deleted = IndexList()
        var moved = FromIndexToIndexList()

        // Loop through the longer list to calculate all changed indexes.
        for (index1, item) in enumerate(beforeIsSmaller ? after : before) {
            if let index2 = map[item] {
                if (index1 != index2) {
                    let (from, to) = beforeIsSmaller ? (index2, index1) : (index1, index2)
                    moved.append((from: from, to: to))
                    map.removeValueForKey(item)
                }
            } else {
                if (beforeIsSmaller) {
                    added.append(index1)
                } else {
                    deleted.append(index1)
                }
            }
        }

        // Handle any indexes still in the map.
        for (_, index) in map {
            if (beforeIsSmaller) {
                deleted.append(index)
            } else {
                added.append(index)
            }
        }

        self.added = added
        self.deleted = deleted
        self.moved = moved
    }
}

let a = ["Anna", "Bob", "Cecilia", "Dennis", "Ellinor", "Frank"]
let b = ["Cecilia", "Bob", "Dennis", "Ellinor", "Gabriella", "Hubert"]

let myDiff = ListDiff<String>(before: a, after: b)
myDiff.added   // [1, 5, 4]
myDiff.deleted // [0, 5]
myDiff.moved   // [(from: 2, to: 0), (from: 3, to: 2), (from: 4, to: 3)]

line 30 must be out the condition.
For testing, use:

let a = ["Roher","Anna", "Bob"]
let b = ["Roher","Cecilia","Anna", "Bob"]