null - NULL 检查中的段错误？

Question

我在尝试检查某些元素是否为 NULL 时遇到段错误或不。任何人都可以帮忙吗？

    void addEdge(int i, int j) 
{
        if (i >= 0 && j > 0) 
    {
        Node* whereto;
        whereto = linkedAdjacencyList[i];
        if(whereto != NULL)
        {
            while(whereto->adj != NULL)
            {whereto = whereto->adj;}
            whereto->adj = linkedAdjacencyList[j];
        }
        else{linkedAdjacencyList[i]->adj = linkedAdjacencyList[j];}
        whereto = linkedAdjacencyList[j];
        if(whereto != NULL)
        {
            while(whereto->adj != NULL)
            {whereto = whereto->adj;}
            whereto->adj = linkedAdjacencyList[i];
        }
        else{linkedAdjacencyList[j]->adj = linkedAdjacencyList[i];}
            }
    }

帮助!

编辑:根据您的建议，这是新代码，但是现在调用该方法时立即出现段错误？我会发布电话...

int edges;
in >> edges;
g.edges = edges;
for(int i = 0; i < edges; i++)
{
    int first;
    int second;
    in >> first >> second;
    g.addEdge(first, second);
}

Answer 1

我建议 linkedAdjacencyList[i]返回 NULL ，所以你试图取消引用 NULL .只需为 NULL 添加额外检查:

Node* whereto = NULL;
whereto = linkedAdjacencyList[i];
if (NULL != whereto){
while(whereto->adj != NULL) .....