Sum of Left Leaves - Solution & Explanation

This approach involves using recursive DFS to traverse the tree. At each node, determine if it is a left leaf. If it is, add its value to the sum and recursively continue to search for more left leaves in the subtree.

We define a helper function dfs which takes a node and a boolean indicating whether it is a left child. If the node is a leaf and is a left child, we add its value to the sum. Otherwise, recurse into the left and right subtrees.

This approach applies iterative DFS using a stack. By exploring each node iteratively, it checks if a node qualifies as a left leaf and accumulates its value to the sum. It manages to mimic a recursive pattern iteratively.

This C solution uses a custom stack to perform an iterative DFS. It pushes nodes onto the stack and processes them. If deemed a left leaf, its value contributes to the sum. By simulating recursion iteratively, this approach eliminates associated stack memory drawbacks.