Decode the Coding Interview in Go: Real-World Examples/

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Invert Binary Tree

Invert Binary Tree

Understand and solve the interview question "Invert Binary Tree".

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Description

In this lesson, your task is to invert a given a binary tree, T.

Let’s look at an example below:

Coding exercise

Go (1.6.2)
package main
import (
  "fmt"
  "strconv"
  "encoding/json"
)
type TreeNode struct{
    val int
    left *TreeNode
    right *TreeNode
}
func invertTree(root *TreeNode) *TreeNode{
    // write your code here
    return root
}
Invert binary tree

Solution

We can solve this problem using depth-first search (DFS).

The inverse of an empty tree is the empty tree. To invert tree T with root and subtrees left and right, we keep root the same and invert the right and left subtrees.

Let’s review the implementation below:

Go (1.6.2)
package main
import (
  "fmt"
  "strconv"
)
type TreeNode struct{
    val int
    left *TreeNode
    right *TreeNode
}
func invertTree(root *TreeNode) *TreeNode{
    if root == nil {
        return root
    }
    right := invertTree(root.right)
    left := invertTree(root.left)
    root.left = right
    root.right = left
    return root
}
func main() {
    root := &TreeNode{val: 1}
    root.left = &TreeNode{val: 2}
    root.right = &TreeNode{val: 3}
    root.left.left = &TreeNode{val: 4}
    root.left.right = &TreeNode{val: 5}
    root.right.left = &TreeNode{val: 6}
    root.right.right = &TreeNode{val: 7}
    print(invertTree(root))
}
Invert binary tree

Complexity measures

Time Complexity Space Complexity
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