面向对象程序设计-C++ Steam & Vector 【第三次上课笔记】

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Conference: http://blog.csdn.net/candy1232009/article/details/7032526

//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;
}