| 1 | export interface TreeData { |
| 2 | parentById: Record<string, string>; |
| 3 | childrenById: Record<string, string[]>; |
| 4 | } |
| 5 | |
| 6 | export const findCommonAncestor = (id1: string, id2: string, { parentById }: TreeData) => { |
| 7 | const visited = new Set(); |
| 8 | let currentId = id1; |
| 9 | |
| 10 | // Edge case with self edges |
| 11 | if (id1 === id2) { |
| 12 | return parentById[id1] || 'root'; |
| 13 | } |
| 14 | |
| 15 | while (currentId) { |
| 16 | visited.add(currentId); |
| 17 | if (currentId === id2) { |
| 18 | return currentId; |
| 19 | } |
| 20 | currentId = parentById[currentId]; |
| 21 | } |
| 22 | |
| 23 | currentId = id2; |
| 24 | while (currentId) { |
| 25 | if (visited.has(currentId)) { |
| 26 | return currentId; |
| 27 | } |
| 28 | currentId = parentById[currentId]; |
| 29 | } |
| 30 | |
| 31 | return 'root'; |
| 32 | }; |
| 33 | |