/**
* {@inheritdoc}
*/
public function calculate($start, $finish)
{
// check if the nodes exist
if (!isset($this->nodes[$start])) {
throw new \InvalidArgumentException("The starting node '" . $start . "' is not found");
}
if (!isset($this->nodes[$finish])) {
throw new \InvalidArgumentException("The ending node '" . $finish . "' is not found");
}
$distances = [];
$distances[$start] = 0;
$visited = [];
$previous = [];
$queue = new PriorityQueue();
$queue->insert($start, $distances[$start]);
$queue->top();
while ($queue->valid()) {
$smallest = $queue->current();
if ($smallest == $finish) {
// trying to make path
$path = array();
while (isset($previous[$smallest])) {
$path[] = $smallest;
$smallest = $previous[$smallest];
}
$path[] = $start;
return ['distance' => $distances[$finish], 'path' => array_reverse($path)];
}
if (isset($visited[$smallest])) {
$queue->next();
continue;
}
$visited[$smallest] = true;
foreach ($this->nodes[$smallest] as $neighbor => $weight) {
if (isset($visited[$neighbor])) {
continue;
}
$alt = $distances[$smallest] + $weight;
if (!isset($distances[$neighbor]) || $alt < $distances[$neighbor]) {
$distances[$neighbor] = $alt;
$previous[$neighbor] = $smallest;
$queue->insert($neighbor, $alt);
}
}
$queue->next();
}
// there is no available path if the graph is unconnected
return null;
}
public function shortest_path($start, $finish)
{
$distances = array();
$previous = array();
$nodes = new PriorityQueue();
foreach ($this->verticies as $vertex => $value) {
if ($vertex === $start) {
$distances[$vertex] = 0;
$nodes->insert($vertex, 0);
} else {
$distances[$vertex] = PHP_INT_MAX;
$nodes->insert($vertex, PHP_INT_MAX);
}
$previous[$vertex] = null;
}
$nodes->top();
while ($nodes->valid()) {
$smallest = $nodes->current();
if ($smallest === $finish) {
$path = array();
while ($previous[$smallest]) {
$path[] = $smallest;
$smallest = $previous[$smallest];
}
$path[] = $start;
$alt = $distances[$finish];
$path['Разстояние'] = $alt;
return array_reverse($path);
}
if ($smallest === null || $distances[$smallest] === PHP_INT_MAX) {
break;
}
foreach ($this->verticies[$smallest] as $neighbor => $value) {
$alt = $distances[$smallest] + $this->verticies[$smallest][$neighbor];
if ($alt < $distances[$neighbor]) {
$distances[$neighbor] = $alt;
$previous[$neighbor] = $smallest;
$nodes->insert($neighbor, $alt);
}
}
$nodes->next();
}
return $distances;
}
