examples: add 2 more graph search examples (DFS and BFS), move them into `examples/graphs` (#14131)
Claudio Cesar de Sá
parent
e0963381ec
commit
7325727e38
GPG Key ID:
B75D4F293C7052DB
|
|
@ -1,3 +1,18 @@
|
|||
fn main() {
|
||||
graph := {
|
||||
'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']
|
||||
}
|
||||
|
||||
// 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{}
|
||||
|
|
@ -24,18 +39,3 @@ fn breadth_first_search_path(graph map[string][]string, vertex string, target st
|
|||
}
|
||||
return path
|
||||
}
|
||||
|
||||
fn main() {
|
||||
graph := {
|
||||
'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']
|
||||
}
|
||||
|
|
@ -0,0 +1,92 @@
|
|||
// Author: ccs
|
||||
// I follow literally code in C, done many years ago
|
||||
fn main() {
|
||||
// Adjacency matrix as a map
|
||||
graph := {
|
||||
'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('\n The shortest path from node A to node F is: $path.reverse()')
|
||||
}
|
||||
|
||||
// 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, start string, target string) []string {
|
||||
mut path := []string{} // ONE PATH with SUCCESS = array
|
||||
mut queue := []string{} // a queue ... many paths
|
||||
// all_nodes := graph.keys() // get a key of this map
|
||||
n_nodes := graph.len // numbers of nodes of this graph
|
||||
// a map to store all the nodes visited to avoid cycles
|
||||
// start all them with False, not visited yet
|
||||
mut visited := a_map_nodes_bool(n_nodes) // a map fully
|
||||
// false ==> not visited yet: {'A': false, 'B': false, 'C': false, 'D': false, 'E': false}
|
||||
queue << start // first arrival
|
||||
for queue.len != 0 {
|
||||
mut node := departure(mut queue) // get the front node and remove it
|
||||
if visited[node] == false { // check if this node is already visited
|
||||
// if no ... test it searchinf for a final node
|
||||
visited[node] = true // means: visit this node
|
||||
if node == target {
|
||||
path = build_path_reverse(graph, start, node, visited)
|
||||
return path
|
||||
}
|
||||
// Expansion of node removed from queue
|
||||
print('\n Expansion of node $node (true/false): ${graph[node]}')
|
||||
// take all nodes from the node
|
||||
for vertex in graph[node] { // println("\n ...${vertex}")
|
||||
// not explored yet
|
||||
if visited[vertex] == false {
|
||||
queue << vertex
|
||||
}
|
||||
}
|
||||
print('\n QUEUE: $queue (only not visited) \n Visited: $visited')
|
||||
}
|
||||
}
|
||||
path = ['Path not found, problem in the Graph, start or end nodes! ']
|
||||
return path
|
||||
}
|
||||
|
||||
// Creating a map for VISITED nodes ...
|
||||
// starting by false ===> means this node was not visited yet
|
||||
fn a_map_nodes_bool(size int) map[string]bool {
|
||||
mut my_map := map[string]bool{} // look this map ...
|
||||
base := u8(65)
|
||||
mut key := base.ascii_str()
|
||||
for i in 0 .. size {
|
||||
key = u8(base + i).ascii_str()
|
||||
my_map[key] = false
|
||||
}
|
||||
return my_map
|
||||
}
|
||||
|
||||
// classical removing of a node from the start of a queue
|
||||
fn departure(mut queue []string) string {
|
||||
mut x := queue[0]
|
||||
queue.delete(0)
|
||||
return x
|
||||
}
|
||||
|
||||
// Based in the current node that is final, search for its parent, already visited, up to the root or start node
|
||||
fn build_path_reverse(graph map[string][]string, start string, final string, visited map[string]bool) []string {
|
||||
print('\n\n Nodes visited (true) or no (false): $visited')
|
||||
array_of_nodes := graph.keys()
|
||||
mut current := final
|
||||
mut path := []string{}
|
||||
path << current
|
||||
|
||||
for (current != start) {
|
||||
for i in array_of_nodes {
|
||||
if (current in graph[i]) && (visited[i] == true) {
|
||||
current = i
|
||||
break // the first ocurrence is enough
|
||||
}
|
||||
}
|
||||
path << current // update the path tracked
|
||||
}
|
||||
return path
|
||||
}
|
||||
|
|
@ -0,0 +1,103 @@
|
|||
// Author: ccs
|
||||
// I follow literally code in C, done many years ago
|
||||
|
||||
fn main() {
|
||||
// Adjacency matrix as a map
|
||||
// Example 01
|
||||
graph_01 := {
|
||||
'A': ['B', 'C']
|
||||
'B': ['A', 'D', 'E']
|
||||
'C': ['A', 'F']
|
||||
'D': ['B']
|
||||
'E': ['F', 'B', 'F']
|
||||
'F': ['C', 'E']
|
||||
}
|
||||
// Example 02
|
||||
graph_02 := {
|
||||
'A': ['B', 'C', 'D']
|
||||
'B': ['E']
|
||||
'C': ['F']
|
||||
'D': ['E']
|
||||
'E': ['H']
|
||||
'F': ['H']
|
||||
'G': ['H']
|
||||
'H': ['E', 'F', 'G']
|
||||
}
|
||||
// println('Graph: $graph')
|
||||
path_01 := depth_first_search_path(graph_01, 'A', 'F')
|
||||
println('\n Graph_01: a first path from node A to node F is: $path_01.reverse()')
|
||||
path_02 := depth_first_search_path(graph_02, 'A', 'H')
|
||||
println('\n Graph_02: a first path from node A to node F is: $path_02.reverse()')
|
||||
}
|
||||
|
||||
// Depth-First Search (BFS) allows you to find a path between two nodes in the graph.
|
||||
fn depth_first_search_path(graph map[string][]string, start string, target string) []string {
|
||||
mut path := []string{} // ONE PATH with SUCCESS = array
|
||||
mut stack := []string{} // a stack ... many nodes
|
||||
// all_nodes := graph.keys() // get a key of this map
|
||||
n_nodes := graph.len // numbers of nodes of this graph
|
||||
mut visited := a_map_nodes_bool(n_nodes) // a map fully
|
||||
// false ... not visited yet: {'A': false, 'B': false, 'C': false, 'D': false, 'E': false}
|
||||
|
||||
stack << start // first push on the stack
|
||||
for stack.len > 0 {
|
||||
mut node := stack.pop() // get the top node and remove it from the stack
|
||||
|
||||
// check if this node is already visited
|
||||
if visited[node] == false {
|
||||
// if no ... test it searchin for a final node
|
||||
visited[node] = true // means: node visited
|
||||
if node == target {
|
||||
path = build_path_reverse(graph, start, node, visited)
|
||||
return path
|
||||
}
|
||||
// Exploring of node removed from stack and add its relatives
|
||||
print('\n Exploring of node $node (true/false): ${graph[node]}')
|
||||
// graph[node].reverse() take a classical choice for DFS
|
||||
// at most os left in this case.
|
||||
// use vertex in graph[node] the choice is right
|
||||
|
||||
// take all nodes from the node
|
||||
for vertex in graph[node].reverse() {
|
||||
// println("\n ...${vertex}")
|
||||
// not explored yet
|
||||
if visited[vertex] == false {
|
||||
stack << vertex
|
||||
}
|
||||
}
|
||||
print('\n Stack: $stack (only not visited) \n Visited: $visited')
|
||||
}
|
||||
}
|
||||
path = ['Path not found, problem in the Graph, start or end nodes! ']
|
||||
return path
|
||||
}
|
||||
|
||||
// Creating a map for nodes not VISITED visited ...
|
||||
// starting by false ===> means this node was not visited yet
|
||||
fn a_map_nodes_bool(size int) map[string]bool {
|
||||
mut my_map := map[string]bool{} // look this map ...
|
||||
for i in 0 .. size {
|
||||
my_map[u8(65 + i).ascii_str()] = false
|
||||
}
|
||||
return my_map
|
||||
}
|
||||
|
||||
// Based in the current node that is final, search for his parent, that is already visited, up to the root or start node
|
||||
fn build_path_reverse(graph map[string][]string, start string, final string, visited map[string]bool) []string {
|
||||
print('\n\n Nodes visited (true) or no (false): $visited')
|
||||
array_of_nodes := graph.keys()
|
||||
mut current := final
|
||||
mut path := []string{}
|
||||
path << current
|
||||
|
||||
for current != start {
|
||||
for i in array_of_nodes {
|
||||
if (current in graph[i]) && (visited[i] == true) {
|
||||
current = i
|
||||
break // the first ocurrence is enough
|
||||
}
|
||||
}
|
||||
path << current // updating the path tracked
|
||||
}
|
||||
return path
|
||||
}
|
||||
Loading…
Reference in New Issue