hhariri

fun sumOfInts(list: List<Int>): Int {
    return list.reduce { (x, y) -> x + y}
}

hhariri

fun nameAndTotalTime_v1(albums: List<Album>): List<Pair<String, Int>> {
    return albums.map {
        var total = 0
        it.tracks.forEach {
            total += it.durationInSeconds
        }
        Pair(it.title,total)
    }
}

hhariri

data class Track(val title: String, val durationInSeconds: Int)

val pinkFloyd = listOf(
        Album("The Dark Side of the Moon", 1973, 2, 1,
                listOf(Track("Speak to Me", 90),
                        Track("Breathe", 163),
                        Track("On he Run", 216),
                        Track("Time", 421),
                        Track("The Great Gig in the Sky", 276),
                        Track("Money", 382),

hhariri

fun topUSandUK_hits_years_v2(albums: List<Album>): List<Int> {
    return albums.filter {
        (it.chartUK == 1 && it.chartUS == 1)
    }.map {
        it.year
    }
}

hhariri

fun <T, R> Collection<T>.map(transform : (T) -> R) : List<R>

hhariri

fun topUSandUK_hits_years_v1(albums: List<Album>): List<Int> {
    val hits = albums.filter {
        (it.chartUK == 1 && it.chartUS == 1)
    }
    val years = ArrayList<Int>()
    hits.forEach {
        years.add(it.year)
    }
    return years;
}

hhariri

fun <T> Collection<T>.filter(predicate: (T) -> Boolean) : List<T> 

hhariri

fun topUSandUK_v4(albums: List<Album>): List<Album> {
    return albums.filter {
        (it.chartUK == 1 && it.chartUS == 1)
    }
}

hhariri

fun topUSandUK_v3(albums: List<Album>): List<Album> {

    val hits = arrayListOf<Album>()
    albums.forEach {
        if (it.chartUK == 1 && it.chartUS == 1) {
            hits.add(it)
        }
    }
    return hits;
}

hhariri

fun topUSandUK_v2(albums: List<Album>): List<Album> {

    val hits = arrayListOf<Album>()
    for (album in albums) {
        if (album.chartUK == 1 && album.chartUS == 1) {
            hits.add(album)
        }
    }
    return hits;
}