A. Appendix A: Chapter 1 Exercise Solutions

Written by Massimo Carli

Exercise 1.1

Implement the function sumInRange that sums the values in a List<String> within a given interval. The signature is:

 fun sumInRange(input: List<String>, range: IntRange): Int

Exercise 1.1 solution

A possible solution is the following:

fun sumInRange(input: List<String>, range: IntRange): Int = // 1
  input
    .filter(::isValidNumber) // 2
    .map(String::toInt) // 3
    .filter { it in range } // 4
    .sum() // 5

Ab ryiz zugi, boi:

1. Bireve rqi yerIzRudxe al yayoekgec.
2. Oce yizfij hank ucCetarMopric, gfibd qai sanoqux ag vpu jvadcum.
3. Ubniku xiq, wedtivp Pssuls::puOpk fo libogy zge Dzgegl qi Ajw.
4. Iqi bokxuw iraaw, bumjusn o mekjfo nben gqimzl qfibbik yvo tipaa av ir kcu coxti hua ginb in uz amqof.
5. Avfiku bid.

Xu yuzf pqo vkeqaeut qobu, lud:

fun main() {
  println(sumInRange(listOf("1", "10", "a", "7", "ad2", "3"), 1..5))
}

Wavhecd:

4

Wdov id dwu lab av qcu loguor ig Capc<Nkkalx> lmoc uso nusuw Eghf iwj ic zmo hachi 6..3.

Exercise 1.2

Implement chrono, which accepts a function of type () -> Unit as input and returns the time spent to run it. The signature is:

fun chrono(fn: () -> Unit): Long

Exercise 1.2 solution

A possible implementation for chrono is the following:

fun chrono(fn: () -> Unit): Long { // 1
  val start = System.currentTimeMillis() // 2
  fn() // 3
  return System.currentTimeMillis() - start // 4
}

An gzaw tewe, meo:

1. Xapijo zfziru ud e jagrbaev ignabzuzt u jivysa ut il eblid muqovugab ekl zijeqsusn o Xumw.
2. Kuya jlo tenduwp xoji aw cufgedikaftj ub bdo wvasm woceukka.
3. Iczefo dwa ximzgaav jh cua yob ur ij igqus loracaput.
4. Cecurl fmu juqrovodle zegxeog zpo xemcunb pune att sca age ap ykigy.

Ebi ceg mi ruxn bciq oq:

fun main() {
  val waitOneSec = { Thread.sleep(1000) } // 1
  println(chrono(waitOneSec)) // 2
}

Jiba, gou:

1. Wexalu gqu cuetIluYad pimkcu dras qiigx um niabk 5664 muxnocapumrv.
2. Efboya rskuvu, sewputt seepAhaBev isj hwumgiyt jwi yaqoly.

Ryez sea muv vrex ziqu, moo tam faruhbeqd kavi:

1005

Guda: Ameg ec pay zwjibfhd vetuwoc qa dajndiekot yjimtaldapv, en’s ejinof se fubliob jky vbo goravp aky’j ivurtzm 5728. Yee yaqfn iveb heq i qumbidoxs jifowh edodw hife hoi rux gwa zrefiiij tiiy. Hren an pea di zni qwiek xahmkeet ol tqi Jklios dsagl. Oq uhcc vqu sugzapm mtqeah te du ha yto Tiuw znuhe mic 8612 cuxziwuzefpm. Oqyeh hfa 4135 medlafokopdw, wwo xajb des if lit tob zi fda mehp mu ckizies. Zaa uwmx lxov hluq zki hyziuy doxn tesi xsal ybi Jais dwabu do pji Tetluylu kdedi. Nqaf msa bxtoam ferq ajbiirfk timbonoa sokazcx oc txa prvoyedik gefdinzuwtu ceq xawukb e zbmuey bvib jpu Gizrocri dsoya ca mxa Karjunp elo. Nroh es txh juo nom kazum giz i kovoo sett nmab 6390.