用vector，如果元素不存在必须push_back()

#include <iostream>
#include <sstream>
#include <vector>
#include <fstream>
#include <string>
using namespace std;

int main(){

    ifstream ifs;
    ifs.open("cpp");
    vector<string> vec_str;//初始化时是空的
    vector<string>::iterator iter = vec_str.begin();
    while(getline(ifs, *iter))//input file to vector    此处产生段错误，因为此时vecs_str是空的,必须在前面定义个string，然后push_back()才可以
    {
        cout<<*iter<<endl;
    }

    return 0;
}

正确的 可以如下：

#include <iostream>
#include <fstream>
#include <string>
#include <sstream>
#include <vector>
using namespace std;

int main(){

    ifstream ofs;
    ofs.open("cpp");
    vector<string> vec_s;
    cout<<"ok"<<endl;
    string ss;
    while(getline(ofs,ss)){
        cout<<"getline"<<endl;
        vec_s.push_back(ss);
        istringstream oss(ss);
        string single;
        while(oss >> single){
            cout<<single<<endl;;
        }
    }

    ofs.close();

    return 0;
}