我对C ++很陌生。
我尝试使用链接节点创建图表的邻接列表实现,在视觉上它看起来像这样:
[Headnode Vertex | Next Node] -> [Adjacent Node Vertex | Next] -> etc
[0 | ]-> [1 | ]-> [2 | ]-> [NULL node]
[1 | ]-> [0 | ]-> [2 | ]-> [NULL node]
[2 | ]-> [0 | ]-> [1 | ]-> [NULL node]
3个节点的图形,顶点编号为0-2,右边?
所以这是我正在实施的代码:
struct node {
int vertex;
node *next;
};
node *headnodes;
bool *Visited;
bool cycles = false;// determine if a graph has cycles.
class Graph {
private:
int n; // number of vertices
int e; // number of edges
//node *headnodes;
public:
Graph(int nodes) // construtor
{
n = nodes;
headnodes = new node[n]; // headnodes is an array of nodes.
for (int i = 0; i < n; i++)
{
headnodes[i].vertex = i;
headnodes[i].next = 0; //points null
}
}
//This function is based off lecture notes (Lecture 13)
//node graph
int Graph::create()
{
//iterate through the head nodes
for (int i = 0; i < n; i++) {
cout << "Initializing " << i << "-th node.\n";
if (i == 0){
//headnode 0 points to its adjacent nodes 1, and 2
headnodes[n].next = new node; //initialize new node
node link = headnodes[n]; //assign to new variable
link.vertex = 1;
link.next->vertex = 2;
link.next->next = 0;
//This works
cout << "vertex of first node: " << headnodes[n].next->vertex;
} else if (i == 1){
headnodes[n].next = new node; //initialize new node
node link = headnodes[n];
link.vertex = 0; //the first node
link.next->vertex = 3; //the second node
//the 3rd node
/*link.next = new node;
node *link2 = link.next;
link.next->next->vertex = 4;
link.next->next->next = 0;*/
} else if (i == 2){
headnodes[n].next = new node; //initialize new node
node link = headnodes[n];
link.vertex = 0;
link.next->vertex = 3;
link.next->next = 0;
}
}
//This doesn't?
cout << "Checking vertex";
cout << "First node's link vert: " << headnodes[0].next->vertex; //ERROR, Access Violation!
return 0;
}
};
我认为,因为headnodes变量是全局的,所以它会很好,但它会导致RunTime错误(访问冲突),显然它指向一个空节点(但它是全局的,所以它是全局的WTH)?我没有弄错。
有人能指出我正确的方向吗?我觉得我很接近。
答案 0 :(得分:1)
你的问题很简单。在create
函数中,您尝试迭代邻接列表,但是您不断索引n-th
headnode
,您可能知道它超出了数组的范围。
您将{3}作为nodes
传递给n
并在循环中继续将其编入headnodes[n]
。您可以在每次cout << n << endl;
访问之前添加headnodes
来验证这一点;你每次都会看到3
。
您可能希望根据i
将它们编入索引,因为它将是迭代索引。