如何在php中计算最长距离和选择最短距离

function dfs($graph, $start, $visited, $distance) {
    $visited[$start] = true;
    foreach ($graph[$start] as $neighbor => $weight) {
        if (!$visited[$neighbor]) {
            $distance = max($distance, dfs($graph, $neighbor, $visited, $distance + $weight));
        }
    }
    $visited[$start] = false;
    return $distance;
}

$graph = [
    'A' => ['B' => 2, 'C' => 3],
    'B' => ['C' => 1, 'D' => 4],
    'C' => ['D' => 2],
    'D' => []
];

$startNode = 'A';
$visited = array_fill_keys(array_keys($graph), false);
$distance = 0;

$longestDistance = dfs($graph, $startNode, $visited, $distance);
echo "最长距离：".$longestDistance;

function dijkstra($graph, $start, $end) {
    $distances = array_fill_keys(array_keys($graph), INF);
    $distances[$start] = 0;
    $visited = [];

    while (count($visited) < count($graph)) {
        $minDistance = INF;
        $minNode = null;

        foreach ($distances as $node => $distance) {
            if (!in_array($node, $visited) && $distance < $minDistance) {
                $minDistance = $distance;
                $minNode = $node;
            }
        }

        if ($minNode === $end) {
            break;
        }

        foreach ($graph[$minNode] as $neighbor => $weight) {
            $newDistance = $minDistance + $weight;
            if ($newDistance < $distances[$neighbor]) {
                $distances[$neighbor] = $newDistance;
            }
        }

        $visited[] = $minNode;
    }

    return $distances[$end];
}

$graph = [
    'A' => ['B' => 2, 'C' => 3],
    'B' => ['C' => 1, 'D' => 4],
    'C' => ['D' => 2],
    'D' => []
];

$startNode = 'A';
$endNode = 'D';

$shortestDistance = dijkstra($graph, $startNode, $endNode);
echo "最短距离：".$shortestDistance;