How do you solve Delete Leaves With a Given Value on LeetCode?

Delete Leaves With a Given Value (LeetCode #1325) can be solved using Brute Force or Optimal Solution. The optimal approach is Optimal Solution with O(n) time complexity and O(h) space complexity. Key insight: Recursive tree traversal is essential for tree problems.

What is the brute force solution for Delete Leaves With a Given Value?

The brute force approach for Delete Leaves With a Given Value is Brute Force, with O(n²) time complexity and O(1) space complexity. In the brute-force approach, we will traverse the tree and check each leaf node. If it matches the target value, we will remove it. This process will continue until no more leaves with the target value are left. The optimal Optimal Solution approach improves this to O(n).

What algorithm or data structure is used to solve Delete Leaves With a Given Value?

Delete Leaves With a Given Value uses the following concepts: Tree, Depth-First Search, Binary Tree. The recommended patterns to study are: Depth-First Search (DFS), Tree Traversal.

What are the interview tips for Delete Leaves With a Given Value?

Explain your thought process clearly while coding. Consider edge cases, such as a tree with only one node. Practice tree traversal techniques to become comfortable with recursive solutions.

What are common mistakes when solving Delete Leaves With a Given Value?

Not handling null cases properly, which can lead to NullPointerExceptions. Failing to check if a parent node becomes a leaf after removing a child.

#1325

Delete Leaves With a Given Value

Medium

TreeDepth-First SearchBinary TreeDepth-First Search (DFS)Tree Traversal

LeetCode ↗

Approaches

Brute ForceOptimal

Complexity Comparison

	Brute Force	Optimal Solution★
Time	O(n²)	O(n)
Space	O(1)	O(h)

💡

Intuition

Time O(n)Space O(h)

The optimal solution also uses DFS but ensures that we only traverse the tree once. We check each node and its children, and if a child is a leaf with the target value, we remove it. This way, we efficiently handle the cascading deletions.

⚙️

Algorithm

5 steps

1Step 1: Start DFS from the root node.
2Step 2: Recursively check the left and right children.
3Step 3: If a child is a leaf node with the target value, return null to its parent.
4Step 4: If the current node has no children left and its value equals target, return null.
5Step 5: Otherwise, return the current node.

solution.py15 lines

1class TreeNode:
2    def __init__(self, val=0, left=None, right=None):
3        self.val = val
4        self.left = left
5        self.right = right
6
7class Solution:
8    def removeLeafNodes(self, root: TreeNode, target: int) -> TreeNode:
9        if not root:
10            return None
11        root.left = self.removeLeafNodes(root.left, target)
12        root.right = self.removeLeafNodes(root.right, target)
13        if root.val == target and not root.left and not root.right:
14            return None
15        return root

ℹ

Complexity note: The time complexity is O(n) because we visit each node exactly once. The space complexity is O(h) due to the recursion stack, where h is the height of the tree.

1Recursive tree traversal is essential for tree problems.
2Understanding leaf nodes and their properties is crucial for this problem.

Solutions and explanations are original Tejav content. Problem titles © LeetCode — use the LeetCode button above for the full problem statement.