BFS

One skeleton, three surfaces: tree, grid, generic graph. The line that makes it work is int size = queue.size(); — freeze it, or your levels bleed into each…

Use a Queue to process all nodes at each depth before moving deeper. Problem walkthrough from the BFS pattern set — Java templates, complexity analysis and…

Same level-order BFS as LC 102, then present levels from leaf to root (bottom-up)

At each depth, the rightmost node (in left-to-right order) is what you see from the right side

For each level, sum all values at that level and divide by the count — use long (or double) for the sum to avoid integer overflow

Minimum depth = shortest path from root to a leaf (node with no children). BFS finds the nearest leaf first; naive DFS can explore deep branches before a…