Skip to content
Snippets Groups Projects
Commit 8bd2a1ec authored by Brady James Garvin's avatar Brady James Garvin
Browse files

Traced BeFS and recursive DFS, implemented BeFS, and discussed admissibility.

parent d42e748d
No related branches found
No related tags found
No related merge requests found
......@@ -113,24 +113,34 @@ Four moves: `123` → `213` → `231` → `312` → `321`
------------ --------------
(⊥, a, 0) → 2 ✓ a → (⊥, a, 0)
(a, c, 7) → 9 ✓ c → (a, c, 7)
(c, e, 12) → 13
(c, b, 8) → 9
(c, e, 12) → 13 ✓ b → (c, b, 8)
(c, b, 8) → 9 ✓ e → (c, e, 12)
(b, e, 17) → 18 d → (e, d, 15)
(b, a, 12) → 14 ✓
(e, d, 15) → 15 ✓
(e, f, 14) → 16
Reversed Path
----
d ← e ← c ← a
## A*
* Worklist:
* Priority:
* Worklist: Priority Queue
* Priority: Distance travelled from the source plus estimated distance to the destination (using an *admissible* heuristic)
* Guaranteed to find a path with least weight
* Can have good best- and average-case time efficiency
## Recursive Depth-First Search (DFS)
* Worklist:
* Worklist: The program stack
Activation Frames Backpointers Returned
----------------------------------- ------------ ----------------
edge = (⊥, a), incidence = …
edge = (⊥, a), incidence = (a, c) a → (⊥, a) [a, c, b, e, f, d]
edge = (a, c), incidence = (c, b) c → (a, c) [c, b, e, f, d]
edge = (c, b), incidence = (b, e) b → (c, b) [b, e, f, d]
edge = (b, a) ⊥
edge = (b, e), incidence = (e, f) e → (b, e) [e, f, d]
edge = (e, f), incidence = (f, d) f → (e, f) [f, d]
edge = (f, d) d → (f, d) [d]
......@@ -90,11 +90,43 @@ export function dijkstras(graph, source, destination) {
}
function heuristic(vertex, destination) {
return 0; // TODO: stub
if ('acf'.includes(vertex)) {
return 2;
}
if ('be'.includes(vertex)) {
return 1;
}
return 0;
}
export function bestFirst(graph, source, destination) {
return undefined; // TODO: stub
const backpointers = new Map();
const worklist = new PriorityQueue();
worklist.insert(new Edge(undefined, source, 0), heuristic(source, destination));
while (worklist.size > 0) {
const workitem = worklist.remove();
if (backpointers.has(workitem.to) &&
backpointers.get(workitem.to).distance <= workitem.distance) {
continue;
}
backpointers.set(workitem.to, workitem);
if (workitem.to === destination) {
const reversedPath = [];
for (let current = destination;
current !== undefined;
current = backpointers.get(current).from) {
reversedPath.push(current);
}
return reversedPath.reverse();
}
for (const incidence of graph.getIncidences(workitem.to)) {
worklist.insert(
new Edge(workitem.to, incidence.destination, workitem.distance + incidence.weight),
workitem.distance + incidence.weight + heuristic(incidence.destination, destination),
);
}
}
return undefined;
}
export function recursiveDFS(graph, source, destination) {
......
......@@ -29,7 +29,7 @@ function formatSolution(solution) {
}
export function Solution(props) {
const search = dijkstras;
const search = bestFirst;
const firstSolution = search(firstExample, 'a', 'd');
const secondSolution = search(secondExample, '123', '321');
return (
......
0% Loading or .
You are about to add 0 people to the discussion. Proceed with caution.
Please register or to comment