C ++計算有向圖中的最短路徑

Question

我的任務是編寫一個程序，以維護簡單網絡的表示（加權有向圖），並根據請求計算兩個給定節點之間的最佳路徑。

當前，我正在嘗試編寫一個函數來計算兩個節點之間最簡單的函數，但是，在嘗試運行程序時，出現兩個特定錯誤

Severity    Code    Description Project File    Line    Suppression State
Error   C3863   array type 'bool [openNode]' is not assignable  P   127 

和

Severity    Code    Description Project File    Line    Suppression State
Error   C3863   array type 'int [openNode]' is not assignable   

我無法調試，因為這兩個主要錯誤不允許我的程序運行。 這些錯誤是否有任何特定原因？

提前致謝！

這是Graph.h中定義的節點結構

struct GraphNode
{
    char ID;
    std::string name;
    int inNodes = 0;
    int outNodes = 0;
    std::vector<std::pair<GraphNode*, int>> connection;
    int  connections = 0;
};

這是導致錯誤的特定代碼。

#include "Graph.h"

std::vector<GraphNode*> _graph;
int openNode = 0;

//Obligatory constructor
void Graph()
{

}

void shortestPath(char fromNode, char toNode)
{
    bool known[openNode];
    int distance[openNode];
    GraphNode*  previous[openNode];
    int numbChecked = 0;


    for (int i = 0; i < openNode; i++)
    {
        known[i] = false;
        distance[i] = 999999;
        previous[i] = nullptr;
    }

    distance[findNode(fromNode)] = 0;

    while (numbChecked < openNode)
    {
        int smallestUnknown = 9999999;
        int locationOfSmall = 0;
        for (int i = 0; i < openNode; i++)
        {
            if (known[i] == false && distance[i] < smallestUnknown)
            {
                smallestUnknown = distance[i];
                locationOfSmall = i;
            }
        }

        if (distance[locationOfSmall] == 0)
        {
            previous[locationOfSmall] = nullptr;
        }

        known[locationOfSmall] = true;
        numbChecked++;

        if (_graph[locationOfSmall]->outNodes > 0)
        {
            for (int i = 0; i < _graph[locationOfSmall]->outNodes; i++)
            {
                int newDistanceLocation = findNode(_graph[locationOfSmall]->connection[i].first->ID);
                if (known[newDistanceLocation] == false && (distance[locationOfSmall] + _graph[locationOfSmall]->connection[i].second) < distance[newDistanceLocation])
                {
                    distance[newDistanceLocation] = distance[locationOfSmall] + _graph[locationOfSmall]->connection[i].second;
                    previous[newDistanceLocation] = _graph[locationOfSmall];
                }
            }
        }
    }

    int destination = findNode(toNode);
    std::string output;
    std::string charTransfer;
    charTransfer = toNode;
    output = charTransfer;

    while (previous[destination] != nullptr)
    {
        destination = findNode(previous[destination]->ID);
        charTransfer = _graph[destination]->ID;
        output = charTransfer + "->" + output;
    }

    if (_graph[destination]->ID != fromNode)
    {
        std::cout << "The nodes are not connected." << std::endl;
    }
    else
    {
        std::cout << "The path is: " << output << std::endl;
        std::cout << "The distance is: " << distance[findNode(toNode)] << std::endl;
    }

}

任何更改建議將不勝感激！

Answer 1

shortestPath函數開頭的代碼無效：

bool known[openNode];
int distance[openNode];
GraphNode*  previous[openNode];

您不能使用變量在堆棧上創建數組（這是您要在其中進行的操作），因為編譯器在編譯時不知道openNode的值（這是確定堆棧大小所必需的）。

為什么不使用向量，例如：

std::vector<bool> known(openNode, false);
std::vector<int> distance(openNode, 999999);
std::vector<GraphNode*>  previous(openNode, nullptr);

使用此方法也會使下面的for循環過時。