c++ - 函数填充 vector ，但它在某个时候变成空的。

Question

我遇到了一个奇怪的问题。我试图用一个函数填充一个 vector ，然后用另一个函数输出它。即使在调用该函数之后，该 vector 仍显示为空，我相信它正在正确填充它。到目前为止，这是我的代码。结果是

"在.txt中输入输入文件名在 vector 中搜索在抛出“std::out_of_range”的实例后调用终止 什么(): vector::_M_range_check中止(核心转储)"

    #include <iostream>
    #include <cassert>

    #include<vector>
    #include "ArrayUtilities.h"


    using namespace std;

    void fillArray(istream& io, std::vector<int> a, int& actualSize)
    {
       int temp,i=0;
       io>>temp;
       while (temp!=-999)
       {
       a.push_back(temp);
           io>>temp;
           i++;
       }

       actualSize=i;
    }



    void outputArray(ostream& os,
            std::vector<int> a,
            const int actualSize,
            const string& info )
    {
os<<info<<"\n";
for (int w=0;w<actualSize;++w)
{
    os<< a.at(w)<<" ";

}
os<<"\n";
}

主要内容(){

int actualSize;
string fileName;
string info;


std::vector<int> a;
cout << "Enter the input file name ";
cin  >> fileName;
ifstream inData;
ofstream outData;
inData.open(fileName.c_str());
outData.open("out.txt");
int searchItem;
inData>>info;
inData>>searchItem;
fillArray  (inData,  a, actualSize);
cout   <<"Search in vector\n";
outData<<"Search in vector\n";
    outputArray(outData, a, actualSize, info);
outputArray(cout,    a, actualSize, info);
//sequential search
int position;
position=seqSearch(a,actualSize,searchItem);
if (position > 0)
    {
        cout    << "Sequential Search: SearchItem "
                << searchItem
                << " is on position "
                << position
                << "\n";
        outData << "Sequential Search: SearchItem "
                << searchItem
                << " is on position "
                << position
                << "\n";
    }
    else
    {
        cout    << "Sequential Search: SearchItem "
                << searchItem
                << " is not in the list\n";
        outData << "Sequential Search: SearchItem "
                << searchItem
                << " is not in the list\n";
    }

谢谢你的帮助

Answer 1

您的函数具有 vector 的本地拷贝。它不影响作为参数传递的 vector 。您可以通过传递对 vector 的引用来解决此问题:

void fillArray(istream& io, std::vector<int>& a, int& actualSize)
//                                          ^