流随机访问

17.39

#include<iostream>

#include<fstream>

#include<string>

#include<cstdlib>

using namespace std;



int main()

{

    fstream inOut("copyOut",fstream::ate|fstream::in|fstream::out);

    if(!inOut)

    {

        cerr<<"Unable to open file!"<<endl;

        return EXIT_FAILURE;

    }

    auto end_mark=inOut.tellg();

    inOut.seekg(0,fstream::beg);

    size_t cnt=0;

    string line;

    while(inOut&&inOut.tellg()!=end_mark&&getline(inOut,line))

    {

        cnt+=line.size()+1;

        auto mark=inOut.tellg();

        inOut.seekp(0,fstream::end);

        inOut<<cnt;

        if(mark!=end_mark)

            inOut<<" ";

        inOut.seekg(mark);

    }

    inOut.seekp(0,fstream::end);

    inOut<<'\n';

    return 0;

}