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Grokking the Coding Interview Patterns in Go

Build Binary Tree from Preorder and Inorder Traversal

Explore how to create a binary tree from preorder and inorder traversal arrays using depth-first search methods. Learn to interpret traversal data, reconstruct the tree structure step-by-step, and practice coding your solution in an interactive environment.

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Statement

Create a binary tree from two integer arrays, pOrder and iOrder, where pOrder represents a preorder traversal of a binary tree, and iOrder represents an inorder traversal of the same tree.

Constraints:

  • 1≤1 \leq pOrder.length, iOrder.length ≤1000\leq1000
  • iOrder.length ==== pOrder.length
  • −1000≤-1000 \leq pOrder[i], iOrder[i] ≤1000\leq 1000
  • pOrder and iOrder consist of unique values.
  • Each value of iOrder also appears in pOrder and vice versa.

Examples

Understand the problem

Let’s take a moment to make sure you’ve correctly understood the problem. The quiz below helps us to check if you’re solving the correct problem:

Build Binary Tree from Preorder and Inorder Traversal

1.

Select the correct binary tree constructed from preorder and inorder traversal:

preorder = [1, 12, 15, 6, 9, 5, 2]

inorder = [15, 12, 6, 1, 5, 9, 2]

A.
    1
   /  \
  12   9
 / \  / \
15  6 5  2
B.
    12
   /  \
  1    9
 / \  / \
15  6 5  2
C.
    15
   /  \
  12   9
 / \  / \
1  6 5   2
D.
    9
   /  \
  1   12
 / \  / \
15  6 5  2
1 / 2

Figure it out!

We have a game for you to play. Rearrange the logical building blocks to develop a clearer understanding of how to solve this problem.

Sequence - Vertical
Drag and drop the cards to rearrange them in the correct sequence.
1
2
3
4
5

Try it yourself

Implement your solution in the following coding playground.

Go
usercode > main.go
package main

import (. "golang-test-code/ds_v1/BinaryTree") // TreeNode[T]



// Definition of a binary tree node 

// type TreeNode[T any] struct {

// 	Data  T

// 	Left  *TreeNode[T]

// 	Right *TreeNode[T]

// }



func buildTree(pOrder []int, iOrder []int) *TreeNode[int] {

	

    // Replace this placeholder return statement with your code

	return &TreeNode[int]{Data: -1}

}
Build Binary Tree from Preorder and Inorder Traversal