examples: add a BFS example for finding the shortest distance between nodes in a graph (#10006)

examples/bfs.v

@@ -0,0 +1,41 @@
+// Breadth-First Search (BFS) allows you to find the shortest distance between two nodes in the graph.
+fn breadth_first_search_path(graph map[string][]string, vertex string, target string) []string {
+	mut path := []string{}
+	mut visited := []string{init: vertex}
+	mut queue := [][][]string{}
+	queue << [[vertex], path]
+	for queue.len > 0 {
+		mut idx := queue.len - 1
+		node := queue[idx][0][0]
+		path = queue[idx][1]
+		queue.delete(idx)
+		if node == target {
+			path << node
+			return path
+		}
+		for child in graph[node] {
+			mut tmp := path.clone()
+			if child !in visited {
+				visited << child
+				tmp << node
+				queue << [[child], tmp]
+			}
+		}
+	}
+	return path
+}
+
+fn main() {
+	graph := map{
+		'A': ['B', 'C']
+		'B': ['A', 'D', 'E']
+		'C': ['A', 'F']
+		'D': ['B']
+		'E': ['B', 'F']
+		'F': ['C', 'E']
+	}
+	println('Graph: $graph')
+	path := breadth_first_search_path(graph, 'A', 'F')
+	println('The shortest path from node A to node F is: $path')
+	assert path == ['A', 'C', 'F']
+}