使用PHP和XML實現資料的有向圖分析

<graph>
    <node id="1" value="A">
        <edge to="2" weight="3" />
        <edge to="3" weight="2" />
    </node>
    <node id="2" value="B">
        <edge to="3" weight="1" />
        <edge to="4" weight="4" />
    </node>
    <node id="3" value="C">
        <edge to="4" weight="2" />
    </node>
    <node id="4" value="D">
        <edge to="1" weight="1" />
    </node>
</graph>

$xml = simplexml_load_file('data.xml');

foreach ($xml->node as $node) {
    $id = $node['id'];
    $value = $node['value'];
    
    // 对节点的操作
    // ...
    
    foreach ($node->edge as $edge) {
        $to = $edge['to'];
        $weight = $edge['weight'];
        
        // 对边的操作
        // ...
    }
}

function traverseGraph($startNode, $visited = []) {
    $visited[$startNode] = true;
    
    echo "Visited node: $startNode
";
    
    global $xml;
    
    foreach ($xml->node as $node) {
        $id = $node['id'];
        
        if ($id == $startNode) {
            foreach ($node->edge as $edge) {
                $to = $edge['to'];
                
                if (!$visited[$to]) {
                    traverseGraph($to, $visited);
                }
            }
        }
    }
}

function findPath($startNode, $endNode, $visited = [], $path = []) {
    $visited[$startNode] = true;
    $path[] = $startNode;
    
    if ($startNode == $endNode) {
        echo "Path found: " . implode('->', $path) . "
";
        return;
    }
    
    global $xml;
    
    foreach ($xml->node as $node) {
        $id = $node['id'];
        
        if ($id == $startNode) {
            foreach ($node->edge as $edge) {
                $to = $edge['to'];
                
                if (!$visited[$to]) {
                    findPath($to, $endNode, $visited, $path);
                }
            }
        }
    }
}

function shortestPath($startNode, $endNode) {
    $distances = [];
    $previous = [];
    $queue = new SplPriorityQueue();
    
    global $xml;
    
    foreach ($xml->node as $node) {
        $id = $node['id'];
        
        if ($id == $startNode) {
            $distances[$id] = 0;
            $queue->insert($id, 0);
        } else {
            $distances[$id] = PHP_INT_MAX;
            $queue->insert($id, PHP_INT_MAX);
        }
        
        $previous[$id] = null;
    }
    
    while (!$queue->isEmpty()) {
        $currentNode = $queue->extract();
        
        foreach ($xml->node as $node) {
            $id = $node['id'];
            
            if ($id == $currentNode) {
                foreach ($node->edge as $edge) {
                    $to = $edge['to'];
                    $weight = $edge['weight'];
                    
                    $newDistance = $distances[$currentNode] + $weight;
                    
                    if ($newDistance < $distances[$to]) {
                        $distances[$to] = $newDistance;
                        $previous[$to] = $currentNode;
                        $queue->insert($to, -$newDistance);
                    }
                }
            }
        }
    }
    
    $path = [];
    $currentNode = $endNode;
    
    while ($currentNode) {
        $path[] = $currentNode;
        $currentNode = $previous[$currentNode];
    }
    
    $path = array_reverse($path);
    
    echo "Shortest path: " . implode('->', $path) . "
";
}