LeetCode/go/all-ancestors-of-a-node-in-a-directed-acyclic-graph.go

package main

func getAncestors(n int, edges [][]int) [][]int {
	fromEdges := func() [][]int {
		neighbours := make([][]int, n)

		for _, edge := range edges {
			u, v := edge[0], edge[1]
			neighbours[u] = append(neighbours[u], v)
		}

		return neighbours
	}

	neighbours := fromEdges()
	ancestors := make([][]int, n)

	var dfs func(int, int)
	dfs = func(ancestor, node int) {
		for _, next := range neighbours[node] {
			vertices := ancestors[next]
			if len(vertices) == 0 || vertices[len(vertices)-1] != ancestor {
				ancestors[next] = append(ancestors[next], ancestor)
				dfs(ancestor, next)
			}
		}
	}

	for i := range n {
		dfs(i, i)
	}

	return ancestors
}