20240402，＜＜，＞＞，控制流：while语句 ，for语句

……学很少，学很慢还是比不学强点是吧，救命
昨天不是很懂<<,>>

输入输出

iostream, 输入流 istream 输出流ostream，COUT,CIN,CERR,CLOG

#include <iostream>
int main() {
	std::cout << "enter two numbers:" << std::endl;
	int v1 = 0, v2 = 0;
	std::cin >> v1 >> v2;
	std::cout << "the sum of" << v1 << " and " << v2 << "is " << v1 + v2 << std::endl;
	std::cout << "the sum of" << v1 << " and " << v2 << "is " << v1 + v2 << "std::endl";
	return 0;
}

1.1 输出运算符<<

接受两个对象，ostream对象<<输出的值：将给定的值写入OSTREAM中

std::cout << "enter two numbers:" << std::endl;
//==(std::cout << "enter two numbers:") << std::endl;

//==std::cout << "enter two numbers:";
//== std::cout << std::endl;

打印ENDL，操纵符，效果是，结束当前行，并将与设备关联的缓冲区中的内容都刷到设备中【保证到目前为止产生的所有输出都能真正写入输出流，而不仅·停留在内存中等待写入流】
：：作用域运算符

1.2 输入运算符>>

接受两个对象，istream>>对象；从给定的ISTREAM读入数据，并写入右侧中；std::cin>>v1；

	std::cin >> v1 >> v2;
	//==(std::cin >> v1) >> v2;
	
	//==std::cin>>v1;
	//==std::cin>>v2;

1.3 注释

/* */注释界定符不能嵌套 

std::cout << "/*";
std::cout << "*/";
std::cout <</*"*/"* / ;
std::cout <</*"*/"/*""/*" * / ;

1.4 控制流

1.4.1 WHILE语句——和C一样咯

#include <iostream>
using namespace std;
int main() 
{
	int sum = 0, val = 1;
	while (val <= 10) {
		sum += val;
		++val;
	}
	cout << "sum of 1 to 10 inclusive is"<<sum << endl;
	return 0;
}

递增也一样，++A，输出之后的，A++，输出之前的 

#include <iostream>
using namespace std;
int main() 
{
	int sum = 0, val = 1;
	while (val <= 10) {
		sum += val;
		cout << ++val << endl;
		//cout << val++ << endl;
	}
	cout << "sum of 1 to 10 inclusive is"<<sum << endl;
	return 0;
}

练习1.9 WHILE50-100整数相加

#include <iostream>
using namespace std;
int main() 
{
	int sum = 50, val = 51;
	while (val <= 100) {
		sum += val;
		 ++val ;
	}
	cout << "sum of 50 to 100 inclusive is "<<sum << endl;
	return 0;
}

练习1.10 递减打印10-1 

#include <iostream>
using namespace std;
int main() 
{
	int val = 10;
	while (val >=0) {
		cout<<val--<<endl ;
	}
	return 0;
}

 练习1.11 指定两个整数之间的所有整数，打印

#include <iostream>//没有比较大小哦，小的在前大的在后
using namespace std;
int main() 
{
	int val1 ,val2;
	cin >> val1 >> val2;
	val1 -= 1;
	while (val1<val2) {
		cout<<val1++<<endl ;
	}
	/*while (val2 - 1 <= val1) {
		cout << val2++ << endl;
	}VAL1的值改变了*/
	return 0;
}

 1.4.2 for语句——和C一样

#include <iostream>
using namespace std;
int main() 
{
	int sum = 0;
	for (int val = 1; val <= 10; ++val)
		sum += val;
	cout << sum << endl;
	return 0;
}

练习1.12  ==0

#include <iostream>
using namespace std;
int main() 
{
	int sum = 0;
	for (int val = -100; val <= 100; ++val)
		sum += val;
	cout << sum << endl;
	return 0;
}

练习1.13 for做9-11

#include <iostream>
using namespace std;
int main() 
{
	int sum = 0;
	for (int val =50; val <= 100; ++val)
		sum += val;
	cout << sum << endl;
	return 0;
}

#include <iostream>
using namespace std;
int main() 
{	
	for (int val = 10; val >= 0; --val)
		cout << val << endl;
	return 0;
}

#include <iostream>
using namespace std;
int main() 
{	
	int v1, v2;
	cin >> v1 >> v2;
	for (int val = v1+1; val < v2; ++val)
		cout << val << endl;
	return 0;
}

今天学点简单的，笑死