Question

因此，我有一个作业，其中有一个转向信号灯，并允许汽车一个一个通过。方向以顺时针顺序更改。我实现了一个代码，该代码读取初始启动方向，每个方向的车辆通过，并读取车牌，方向和通过时间。从E到S到W到N时会发生问题，但是它卡住了，我遇到矢量超出范围

#include <iostream>
#include <vector>
#include <queue>
using namespace std;

struct cars
{
    string name;
    char dr;
    int t;
};

bool init(vector<cars> &arr, char direct)
{
    for (auto i = 0; arr.size(); i++)
    {
        if (arr.at(i).dr == direct)
        {
            return true;
        }
    }
    return false;

}

char direct_shift(char e)
{
    if (e == 'N')
    {
        return 'E';
    }
    else if (e == 'E')
    {
        return 'S';
    }
    else if (e == 'S')
    {
        return 'W';
    }
    else if (e == 'W')
    {
        return 'N';
    }
    else
    {
        return '\0';
    }
}


int main() {

    vector <cars> keeper;
    queue <cars> que;

    char track;  //starting direction
    int car_num;    //starting car num

    string n;
    char d;
    int sec;
    cin >> track;
    cin >> car_num;

    while (cin >> n >> d >> sec) //takes the input if plate, direction and time
    {
        cars temp;
        temp.name = n;
        temp.dr = d;
        temp.t = sec;
        keeper.push_back(temp);
    }

    for (int i = 0; i < keeper.size(); i++) {
        cout << keeper[i].name << " " << keeper[i].dr << " " << keeper[i].t << endl;
    }  //checks if it all inputted it
    char curr_dir = track;

    while (not keeper.empty())
    {
        for (auto i = 0; i < keeper.size(); i++) {
        reset:
            if (init(keeper, curr_dir) == true)
            {
                if (keeper[i].dr == curr_dir) {
                    que.push(keeper.at(i)); //pushes vector at i into queue
                    keeper.erase(keeper.begin() + i); // deletes vector at index i
                    cout << que.front().name << " Going to " << que.front().dr << " at " << que.front().t << endl;
                    que.pop();
                    curr_dir = direct_shift(curr_dir);
                    break;
                }
            }
            else
            {
                curr_dir = direct_shift(curr_dir);
            }
        }
    }
}

Answer 1

由于以下功能，我认为您遇到了问题：

bool init(vector<cars> &arr, char direct) {

  for (auto i = 0; arr.size(); i++) {
       if (arr.at(i).dr == direct) { 
            return true; 
        } 
   } return false; 

}

如果尝试访问不存在的索引，

arr.at(i)将引发out_of_range异常。这意味着在访问索引之前，您需要确保向量不为空/大小不超过

。

bool init(vector<cars> &arr, char direct) { 
     //the loop now checks for (!arr.empty()) 
         for (vector<cars>::size_type i = 0; i <arr.size(); ++i) { 
             if (arr.at(i).dr == direct) {
                  return true; } 
          } return false; 

}

C ++向量超出范围，带有移位变量

1 个答案: