c++向量元素访问

Question

I am trying to create a vector with a datatype I have already defined in a class

vector<MYdatatype> myVector;

but when I try to access the elements in the vector using a for loop

for(int i=0; i<myVector.size();i++)

I get an error message telling that the vector is out of range Debug assertion failed line 932!

THIS IS MY CODE

vector <Road_Segment> Unvisited;//the vector

for (i = 0; i<Unvisited.size(); i++)
{
    cur_node = Unvisited[0];//current node to visit

    find_node_neighbers(cur_node.end_station.ID, end, T_R);

when I try to comment this for loop I don't get that error message

any help would be appreciated

Answer 1

This line:

cur_node = Unvisited[0];

should really be:

cur_node = Unvisited[i];

Otherwise, it will just access the first element over and over.

But if you just need to perform an action on each element, you should use a foreach loop instead:

for (const Road_Segment& cur_node : Unvisited) {
  // I'm guessing "neighbers" is just a typo, but that's what was in the question
  find_node_neighbers(cur_node.end_station.ID, end, T_R);
}

This allows you to avoid any problems with indices and such. Or if you need to actually modify each element instead of just using it, simply remove the const :

for (Road_Segment& cur_node : Unvisited) {
  // do something that modifies cur_node
}