C++Primer第五版:1.12 1.13 1.14 1.16

练习1.12：-100到100的值的和

练习1.13

#include<iostream>
using namespace std;

int main()
{
    
    //1.9
	int sum = 0;

	for (int val = 50; val <= 100; ++val)
		sum += val;
	cout << sum << endl;

	return 0;
}

#include<iostream>
using namespace std;

int main()
{
    
    //1.10
	for (int val = 10; val >= 0; --val)
		cout << val << ' ';
	cout << endl;

	return 0;
}

#include<iostream>
using namespace std;

int main()
{
    
    //1.11
	int val1, val2;

	cout << "Please input two integer:" << endl;
	cin >> val1 >> val2;

	for (; val1 <= val2; ++val1)
		cout << val1 << ' ';
	cout << endl;

	return 0;
}

练习1.14：
1.for循环适用于循环次数已知的情况且变量初始化和判定都在头部
2.while循环适用于循环次数未知的情况

练习1.16

#include<iostream>
using namespace std;

int main()
{
    
    
	int sum = 0;
	int val;

	while (cin >> val)
		sum += val;

	cout << sum << endl;

	return 0;
}