Top View of Binary Tree in DSA Go - Interactive Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to create a new queue for BFS traversal.

DSA Go

queue := make(chan *Node, [1])

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A0

B1

C100

D10

Attempts:

3 left

💡 Hint

Common Mistakes

Using zero capacity channel causes deadlock.

Using capacity 1 is too small for BFS queue.

We create a buffered channel with capacity 10 to hold nodes during BFS.

2fill in blank

medium

Complete the code to update the horizontal distance map only if the distance is not already present.

DSA Go

if _, ok := hdMap[hd]; ![1] { hdMap[hd] = node.data }

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Aok

Bexists

Cfound

Dpresent

Attempts:

3 left

💡 Hint

Common Mistakes

Using variable names other than 'ok' for map presence check.

Not negating the condition to insert only once.

The idiomatic way in Go to check map presence is using 'ok'.

3fill in blank

hard

Fix the error in the BFS loop to correctly update horizontal distance and enqueue children.

DSA Go

for len(queue) > 0 {
    node := <-queue
    hd := [1][node]
    if _, ok := hdMap[hd]; !ok {
        hdMap[hd] = node.data
    }
    if node.left != nil {
        queue <- node.left
        [2][node.left] = hd - 1
    }
    if node.right != nil {
        queue <- node.right
        hdDist[node.right] = hd + 1
    }
}

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AhdMap

BhdDist

Cdistance

Dhd

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'hdMap' to store horizontal distances causes wrong data.

Not updating horizontal distances for children.

We use 'hdDist' map to track horizontal distances of nodes, not 'hdMap' which stores data.

4fill in blank

hard

Fill both blanks to correctly initialize the horizontal distance map and enqueue the root node.

DSA Go

hdDist := make(map[*Node]int)
hdDist[[1]] = 0
queue <- [2]

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Aroot

Bhead

CrootNode

Dstart

Attempts:

3 left

💡 Hint

Common Mistakes

Using different variable names for root causes errors.

Not initializing horizontal distance for root.

We set the root node's horizontal distance to 0 and enqueue the root node.

5fill in blank

hard

Fill all three blanks to print the top view nodes in order of horizontal distance.

DSA Go

keys := make([]int, 0, len(hdMap))
for k := range hdMap {
    keys = append(keys, k)
}
sort.[1](sort.IntSlice(keys))
for _, k := range keys {
    fmt.[2](hdMap[k], " ")
}
fmt.[3]()

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ASortInts

BPrintln

CPrint

DSort

Attempts:

3 left

💡 Hint

Common Mistakes

Using wrong sort function causes compile error.

Using fmt.Println inside loop prints each node on new line.

We use sort.Sort with sort.IntSlice, print with fmt.Print, and end line with fmt.Println.