int main (int argc, char ** argv) some interpretation

#include <iostream>
#include <fstream>
#include <string>
#include <cstdlib>
#include <vector>
#include <algorithm>
#include <iterator>
#include <functional>

using namespace std;
using namespace std::placeholders;

struct CoreUser {
    string user;
    double cost;
};

istream& operator>>(istream& in, CoreUser& core) {
    in >> core.user >> core.cost;
    return in;
}

struct SortUser {
        bool operator()(const CoreUser& u1, const CoreUser& u2) {
            return u1.cost < u2.cost;
            }
};

int main(int argc, char **argv) {
    if (argc < 2)
        return EXIT_FAILURE;
    ifstream in{argv[1]};
    if (!in)
        return EXIT_FAILURE;

    CoreUser u;
    vector<CoreUser> v;

    while (in >> u) {
        v.push_back(u);
    }

    // type your code bellow.
    vector<CoreUser>::iterator ite = v.begin();
    for(;ite < v.end();ite++){
        if((*ite).cost < 24.0){
            v.erase(ite);
        }
    }
    SortUser sortuser;
    sort(v.begin(), v.end(), sortuser);
    for(int i = 0;i < v.size();i++)
        cout<<v[i].user<<"  "<<v[i].cost<<endl;
    in.close();
}

The interpretation of the int main (int argc, char * argv []) in the parameters and argv arg

With a parameter of the main functions, such as main (int argc, char * argv [], char ** env), is UNIX, Linux, and Mac OS operating system, C / C ++ main function standard wording, and is the origin purest The main function of writing.

argc, argv specific meaning:

argc: (argument count) int type argc, commands sent to the main function of the number of line parameters to run statistical procedures, the default value is 1 in VS.

argv: (argument vector) char * type the argv [], an array of strings, used to store a pointer to an array of string parameters, each element pointing to a parameter.

　　　　argv [0]: pointing running full path name

　　　　argv [1]: The first point to a string in the DOS command line execution program name

　　　　argv [2]: after the execution of the program name points to the second string

　　　　argv [3]: after the execution of the program name pointing to third string　　　　

　　　　argv [argv]: is NULL

argv [0] Representative 123.exe argv [1] in the program representative of total.txt

 

 There are two methods to import total.txt

1.cmd  ---demo.exe  total.txt

2.>g++ -std=c++11 demo.cpp -o 123.exe  -----   >dir  ----  >123.exe total.txt