Largest Tree in a Forest

Problem: Largest Tree in a Forest You are given a dictionary/mapping child -> parent, representing parent-child relationships in a forest. Find the root node ID of the tree with the largest number of nodes. If multiple trees tie for the largest size, return the smallest root node ID among them. A root is a node that has no parent, meaning it appears in the parent set but does not appear in the child set. Example Mapping: {1: 2, 3: 8} This means: Node 1's parent is 2. Node 3's parent is 8. The forest contains two trees: 2 -> 1 and 8 -> 3. Both have size 2, so return the smaller root ID: 2 Input Format The first line contains an integer n, the number of child -> parent relations. The next n lines each contain two integers: child parent meaning parent is the parent of child. Output Format Print one integer: the root node ID of the largest tree. If n = 0, there is no node information, so print -1. Constraints and Assumptions 0 <= n <= 100000 Node IDs are integers in [-10^9, 10^9]. The input forms a valid forest: There are no cycles. Each child has at most one parent. Only nodes appearing in the input relations are counted; isolated nodes that do not appear in the input are unknown and should not be considered. Sample Input 2 1 2 3 8 Sample Output 2 Example Input 2 1 2 3 8 Output 2