Display and add methods for adjacency list graph

问题

This is my third time for creating a graph using adjacency list in c++. It's important to use OOP. I feel like the answer to this problem is really simple, but I can't manage to fix and improve my code.

There is it:

#include <iostream>
#include <algorithm>
#include <fstream> 
#include <vector>


using namespace std;
struct Edge
{
    int begin;
    int end;
};

class Graph
{
private:
    int numOfNodes;
    vector<vector<int>> baseVec;

public:
    Graph(int numOfNodes)
    {   

        //baseVec->resize(numOfNodes, vector<int>(numOfNodes));
        for (int i = 0; i < numOfNodes; i++)
        {
            vector<Edge> subVec;
            baseVec.emplace_back(subVec);
        }
    }

    void newEdge(Edge edge)
    {
        if (edge.begin >= numOfNodes && edge.end >= numOfNodes)
        {
            cout << "Invalid edge!\n";
        }
        baseVec[edge.begin].emplace_back(edge.end);
        baseVec[edge.end].emplace_back(edge.begin);
    }
    void display()
    {
        cout << baseVec.size();
        for (int i = 0; i < baseVec.size(); i++)
        {
            cout << "\n Adjacency list of vertex " << i << "\n head ";
            for (int j = 0; j < baseVec[i].size(); j++)
            {
                cout << baseVec[i][j];
                cout << endl;
            }
        }
    }

};

int main()
{
    int vertex, numberOfEdges, begin, end;
    cout << "Enter number of nodes: ";
    cin >> vertex;
    numberOfEdges = vertex * (vertex - 1);

    Edge edge;
    Graph g1(vertex);
    for (int i = 0; i < numberOfEdges; i++)
    {
        cout << "Enter edge ex.1 2 (-1 -1 to exit): \n";
        cin >> edge.begin >> edge.end;
        if ((begin == -1) && (end == -1))
        {
            break;
        }
        g1.newEdge(edge);
    }
    g1.display();
    return 0;
}

So now in Visual Studio I have an error:

'std::vector>::vector(const std::vector<_Ty,std::allocator<_Ty>> &)': cannot convert argument 1 from 'std::vector>' to 'const _Alloc &'

Also that in display() method there is signed/unsigned mismatch. I don't know If there is something wrong with my methods but I'm stuck here.

回答1:

vector<vector<int>> baseVec;

accepts vector<int>s

vector<Edge> subVec;
baseVec.emplace_back(subVec);

Attempts to feed it vector<Edge>s. This does not make sense.

vector<vector<Edge>> baseVec;

Makes better sense.

Note that this change will set up another blast of errors when

cout << baseVec[i][j];

tries to print an edge and does not know how. Either make an operator<< overload to handle edge or change what you're outputting.

来源：https://stackoverflow.com/questions/53326934/display-and-add-methods-for-adjacency-list-graph

标签

c++

class

graph-theory

adjacency-list