Question

为什么我在Adjacency List的C ++实现中出现分段错误？我的printList()功能或其中一个 getter 和 setter 功能有问题吗？相同的实现在Java中工作，但在C ++中不工作。

    #include<iostream>
    #include<list>
    using namespace std;

    class Graph
        {
            int V;
            list<int> *adj;
        public:
            Graph(int V)
                {
                this->V = V;
                adj = new list<int>[V];
                }
            void addEdge(int u, int v)
                {
                this->adj[u].push_back(v);
                }

            int getVertexCount()
                {
                return this->V;
                }

            list<int>* getList()
                {
                return this->adj;
                }
        };

    void printList(Graph g)
        {
        list<int> *adj = g.getList();
        list<int>::iterator it;
        for(int i=0; i< g.getVertexCount(); i++)
                {
                cout << "Adjacency list of vertex " << i << "is:" <<endl;
                for(it=adj[i].begin(); it != adj[i].end(); it++)
                        {
                        cout << *it << "->";
                        }
                }
        }

    int main()
        {
        Graph g(7);
        g.addEdge(0,1);
        g.addEdge(0,2);
        g.addEdge(0,3);
        g.addEdge(1,5);
        g.addEdge(1,6);
        g.addEdge(2,0);
        g.addEdge(2,4);
        g.addEdge(2,6);
        g.addEdge(3,0);
        g.addEdge(3,5);
        g.addEdge(3,7);
        g.addEdge(4,2);
        g.addEdge(4,7);
        g.addEdge(5,3);
        g.addEdge(5,7);
        g.addEdge(6,1);
        g.addEdge(6,2);
        g.addEdge(7,5);
        g.addEdge(7,3);
        g.addEdge(7,4);

        printList(g);

        return 0;
        }

Answer 1

问题在于分配7个条目：

Graph g(7);

后来访问第8个

g.addEdge(7,4);

更好，更灵活

#include <iostream>
#include <list>
#include <vector>

using namespace std;

class Graph {
    vector< list<int> > adj;
  public:
    Graph( void ) {}

    void addEdge( int u, int v ) {
      if ( u > ( ( int )( adj.size() ) - 1 ) ) {
        adj.resize( u + 1 );
      }
      adj[u].push_back( v );
    }

    int getVertexCount() const {
      return adj.size();
    }

    const vector< list<int> >& getList() const {
      return adj;
    }
};

void printList( const Graph& g ) {
  const vector< list<int> >& adj( g.getList() );
  list<int>::const_iterator it;
  for ( int i = 0; i < g.getVertexCount(); i++ ) {
    cout << "Adjacency list of vertex " << i << " is:";
    for ( it = adj[i].begin(); it != adj[i].end(); it++ ) {
      cout << *it << "->";
    }
    cout << endl;
  }
}

int main() {
  Graph g;
  g.addEdge( 0, 1 );
  g.addEdge( 0, 2 );
  g.addEdge( 0, 3 );
  g.addEdge( 1, 5 );
  g.addEdge( 1, 6 );
  g.addEdge( 2, 0 );
  g.addEdge( 2, 4 );
  g.addEdge( 2, 6 );
  g.addEdge( 3, 0 );
  g.addEdge( 3, 5 );
  g.addEdge( 3, 7 );
  g.addEdge( 4, 2 );
  g.addEdge( 4, 7 );
  g.addEdge( 5, 3 );
  g.addEdge( 5, 7 );
  g.addEdge( 6, 1 );
  g.addEdge( 6, 2 );
  g.addEdge( 7, 5 );
  g.addEdge( 7, 3 );
  g.addEdge( 7, 4 );

  printList( g );

  return 0;
}

玩得开心。

邻接列表的C ++实现出错

1 个答案: