Path Sum Root to Leaf in Binary Tree in DSA Javascript - Cheat Sheet & Quick Revision

Recall & Review

beginner

What does the 'Path Sum Root to Leaf' problem ask you to find in a binary tree?

It asks whether there is a path from the root node to any leaf node such that the sum of the node values along that path equals a given target sum.

beginner

In the context of 'Path Sum Root to Leaf', what is a leaf node?

A leaf node is a node in a binary tree that has no children (no left or right child).

intermediate

Why do we subtract the current node's value from the target sum when moving down the tree?

Because we want to check if the remaining sum needed to reach the target can be found in the subtree below the current node.

intermediate

What is the base case for the recursive solution to the Path Sum problem?

When the current node is null, return false. When the current node is a leaf, check if its value equals the remaining sum.

beginner

How does the algorithm decide to return true or false?

It returns true if any path from root to leaf sums to the target; otherwise, it returns false after checking all paths.

What is the first step in checking for a path sum in a binary tree?

A Return true immediately

B Add the current node's value to the sum

C Check if the current node is null

D Check if the current node has children

We first check if the current node is null to handle the base case and avoid errors.

When do we check if the current node's value equals the remaining sum?

A After visiting all nodes

B When the node has children

C At the root node only

D When the node is a leaf node

We check this at leaf nodes because only root-to-leaf paths count.

If the target sum is 22 and the root node value is 5, what sum do we look for in the subtrees?

A 17

B 27

C 22

D 5

We subtract the root value (5) from the target sum (22) to get 17 for the subtrees.

What does it mean if the function returns true at any point?

A A valid path sum has been found

B No path sum exists

C The tree is empty

D The target sum is zero

Returning true means a root-to-leaf path with the target sum exists.

Which traversal method is commonly used to solve the Path Sum problem?

A Breadth-first search (BFS)

B Depth-first search (DFS)

C Level order traversal

D Inorder traversal only

DFS is used to explore each path from root to leaf.

Explain how you would check if a binary tree has a root-to-leaf path with a given sum.

Think about how to reduce the problem as you go down the tree.

Describe the base cases needed in a recursive solution for the Path Sum problem.

Consider what happens when you reach the end of a path.