Algorithms

Recursive mapping: Right and Left views of Binary Trees

Apr 2026

7 min read

Visualizing a tree from the side requires more than just traversal; it requires tracking the 'first' or 'last' node seen at every vertical level of the structure.

Implementation

java

class Solution {
    // Right View: The last node seen at each level
    public List<Integer> rightSideView(TreeNode root) {
        List<Integer> result = new ArrayList<>();
        solve(root, 0, result);
        return result;
    }

    private void solve(TreeNode node, int level, List<Integer> res) {
        if (node == null) return;

        // If this is the first time we've reached this depth,
        // it must be the right-most node
        if (level == res.size()) {
            res.add(node.val);
        }

        solve(node.right, level + 1, res);
        solve(node.left, level + 1, res);
    }
}