面向对象程序设计-C++ Steam & Vector 【第三次上课笔记】

//ofstream fout;    //C style
//fout.open("fout.txt");

ofstream fout ("fout.txt");    //C++ out stream recommend
ifstream fin ("fio.cpp");    

//fout.close()    //Not necessary in C++, because C++ do it automatically

//Copy the whole file

int main(){
    ofstream fout ("SourceCodeCopy.cpp");
    ifstream fin ("SourceCode.cpp");
    string str;
    while(getline(fin, str)){    //Discards newline char
        fout << str << endl;    //... must add it back
    }
    return 0;
}

//calculate the average number

int main(){
    int i, num, cur;
    cin >> num;
    
    //double* array = (double*) malloc(num * sizeof(double));    //C style
    double* array = new double[num];    //C++ style
    double ave = 0.0;
    for(i = 0; i < num; ++i){
        cin >> array[i];
        ave += array[i];
    }
    cout << "Ave is the " << ave / num << endl;
    //free(array);    //C style
    delete[] array;    //[] means delete all the Array, if "delete array" means delete only the array[0]

    return 0;
}

//one double number array Example

int main(){
    double* pd = new double;

    cin >> *pd;
    cout << *pd;
    delete pd;

    return 0;
}

//Introduce Vector

int main(){
    vector <double> vc;        //init a vector
    vc.push_back(27.8);        //insert element to its tail
    vc.push_back(54.2);

    //vc[2] = 89.3    //Don‘t do in this way, no such spacez

    for(i = 0; i < vc.size(); ++i){
        cout << vc[i] << endl;
    }
    return 0;
}

//Answer is 0 0 89.3 27.8 54.2  (5 elements)

int main(){
    int i;
    vector <double> vc(3);    //init a space long for 3 
    vc.push_back(27.8);
    vc.push_back(54.2);

    vc[2] = 89.3;//

    for(i = 0; i < vc.size(); ++i){
        cout << vc[i] << endl;
    }

    return 0;
}

//Copy an entire file into a vector of string

int main(){
    vector <string> v;
    ofstream out ("SourceCodeCopy.cpp");
    ifstream in ("SourceCode.cpp");
    string line;
    while(getline(in, line)){
        v.push_back(line);
    }
    for(int i = 0; i < v.size(); ++i){
        out << 1 + i << ": " << v[i] << endl;
    }

    return 0;
}

//Class work
//give a number N, and make n random numbers into a file

int main(){
    srand((int)time(NULL));
    int i, n;
    vector <int> v;
    ofstream out ("rand_num.txt");
    
    cin >> n;
    while(n--){
        v.push_back(rand() % 65536);
    }
    for(i = 0; i < v.size(); ++i){
        out << v[i] << endl;
    }

    return 0;
}

//make n numbers in the range [0, 1)

int main(){
    srand((int)time(NULL));
    int i, n;
    vector <double> v;
    ofstream out ("rand_num.txt");
    
    cin >> n;
    while(n--){
        v.push_back((double)rand() / (double)RAND_MAX);
    }
    for(i = 0; i < v.size(); ++i){
        out << v[i] << endl;
    }

    return 0;
}