From 92c5bae5aa446ad727dfd0e94ec5044a30d1de00 Mon Sep 17 00:00:00 2001
From: Matej Focko <me@mfocko.xyz>
Date: Sat, 29 Jun 2024 14:11:16 +0200
Subject: [PATCH] =?UTF-8?q?go:=20add=20=C2=AB2192.=20All=20Ancestors=20of?=
 =?UTF-8?q?=20a=20Node=20in=20a=20Directed=20Acyclic=20Graph=C2=BB?=
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Signed-off-by: Matej Focko <me@mfocko.xyz>
---
 ...s-of-a-node-in-a-directed-acyclic-graph.go | 34 +++++++++++++++++++
 1 file changed, 34 insertions(+)
 create mode 100644 go/all-ancestors-of-a-node-in-a-directed-acyclic-graph.go

diff --git a/go/all-ancestors-of-a-node-in-a-directed-acyclic-graph.go b/go/all-ancestors-of-a-node-in-a-directed-acyclic-graph.go
new file mode 100644
index 0000000..708fbe8
--- /dev/null
+++ b/go/all-ancestors-of-a-node-in-a-directed-acyclic-graph.go
@@ -0,0 +1,34 @@
+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
+}