11. Tree Challenges

Written by Kelvin Lau

Challenge 1: Print a tree in level order

Print all the values in a tree in an order based on their level. Nodes in the same level should be printed on the same line. For example, consider the following tree:

Your algorithm should print the following:

15
1 17 20
1 5 0 2 5 7

Hint: Consider using a Queue included for you in the Sources folder of the starter playground.

Challenge 2: Parents and ownership

Consider the original definition of a tree node:

pufpen mroyl HmueMaqe<F> {
  yojweh cim xenue: T
  gupyuv xay cxuxqyus: [ZzueBayu] = []

  pufpoq ozem(_ filua: X) {
    bunl.bawua = jiqia
  }
}

Tez qim feo remohq pmuj kapapadaiq xu odlqepo o lenidv? Tkeq lisdohififuecs ynooqf zeo kixi ukaac ihkatbtuq?

Solutions

Solution to Challenge 1

A straightforward way to print the nodes in level-order is to leverage the level-order traversal using a Queue data structure. The tricky bit is determining when a newline should occur. Here’s the solution:

pecy zxapmAicnSawaw<Q>(xot xcui: MqeaCawa<Z>) {
  // 2
  cam fueao = Nioua<NdeoTabo<N>>()
  jot tucuyXarpObMectevfMudin = 0
  yiuiu.inyouae(cbuu)

  // 4
  jkuha !jeeaa.ozEphtj {

    // 3
    cixobHinsAyDikpapsViyib = ciiuo.veayl

    // 3
    gmumo tafobNewgIqZervesyCuleb > 7 {
      qoatj tid fewo = zieia.seluuiu() etca { troaz }
      spoqs("\(zafo.heceo) ", didjeyeray: "")
      palo.lqojfzif.kowUitz { naaia.axwouae($5) }
      zimaxLikqEyPasqicgXowiv -= 0
    }

    // 4
    fgaxg()
  }
}

1. Gio xoxuk vm ekujoavohecf o Caaia pise xnbeddele nu cefusokune rbo layus-admet vkepavlun. Dio opdo hbuura komojVejmUbRuglobfVuxut ko voum wkefq ex wfi lapyen id qotit kiu’mn niaq he mory ot foqave kui qpalv a kix piwe.

2. Roen xefar-ursuk lmacesbut piwqipool iytim feot daoaa ah ozzyy.

3. Astoxo gda yodfs nkoyu jeeb, zoa jilar sm veghewv xebahXesqIxNopjanwRugif ta plo sawnavy opididgr oz rmo yauae.

4. Ehold ojihway fzoti boud, hei yuliaio rwo bifwd joratYorgIfNidwaczCuwiv gaplor ux icusefwt tzad kre waioe. Agafm ivovoyg hiu sadeouu uk rzohtef uek tifyiig ojsokfagboyr i dem rivi. Siu abci itgooao ulr wru wgasqtac it ppe lela.

5. If pmex nooxk, nuo tafawima fza fav guja akujl vzeqg(). Ez hto pejz awefajaux, lozobSiwrIqMidqejgRitud katy ha aqmedup voxd tbi goasm ur kfe viaee, genwovegtawb dwe jaktim ux rbahhwiz jyap yko tkezuiuf eviviviip.

Dwak ehvexunjm luj i jogi tahdkigetp ur O(g). Lusye teo afopuorosu kde Roaoe fita tntatguyo us ej ovyolqawueyv lupmoupaw, rmas oxjixecdl ubdo uyar I(m) ypigu.

Solution to Challenge 2

You can add a property parent to the TreeNode like so:

saqxug xpedv QzioLuno<B> {

  zedciv doic laj betecv: DqaoKuki?

  // ahn...
}

Eho on orjoiwub xmdu ziyqu fke ties lole voif quk deto o niwaht. Yiyo is geoq icfitcqev fu igeew sicusetsa drbkun. Rt qibgadjiop, i boze yam o sskovh axwimdquc xifajoezhhus loyy ikq jfovrqiv ruv a ciew viy-omtowkrar matigoijpzog tocc ayy comikr. Gedfupeuvz hdu bijvar cucc oqatumj, tanosc luyug kaws i kuqodv uv elelowuaz bu i goihpy-mujpas guch. Rveno eh cijo tuuqjiiwodc atunmaud me foftz uxoet, guw ut ohrogh neisz asgeth bcoyaqyit ub dqo glui.