Binary Tree

Question 1

144. Binary Tree Preorder Traversal

Given a binary tree, return the preorder traversal of its nodes’ values.

Example:

Input: [1,null,2,3]
   1
    \
     2
    /
   3

Output: [1,2,3]

TC - O(n)
SC - O(n)

Answer 1

Pseudo Code:

1. Visit Node.
2. Traverse Left.
3. Traverse Right.

Question 2

94. Binary Tree Inorder Traversal

Given a binary tree, return the inorder traversal of its nodes’ values.

Example:

Input: [1,null,2,3]
   1
    \
     2
    /
   3

Output: [1,3,2]

TC - O(n)
SC - O(n)

Answer 2

Pseudo Code:

1. Traverse Left.
2. Visit Node.
3. Traverse Right.

Question 3

145. Binary Tree Postorder Traversal

Given a binary tree, return the postorder traversal of its nodes’ values.

Example:

Input: [1,null,2,3]
   1
    \
     2
    /
   3

Output: [3,2,1]

TC - O(n)
SC - O(n)

Answer 3

Pseudo Code:

1. Traverse Left.
2. Traverse Right.
3. Visit Node.