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)

#include <iostream>
#include <cstdlib>
#include <ctime>
#include <fstream>
#include <string>
#include <vector>
#include <cmath>
#include <algorithm>

using namespace std;

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;
}