C++ Primer:Exercises Section 1.4.3

Exercise 1.14:如果输入值相等，本节展示的程序将产生什么问题?

#include <iostream>
int main()
{
	std::cout << "Enter two numbers:" << std::endl;
	int v1, v2;
	std::cin >> v1 >> v2; // read input
	// use smaller number as lower bound for summation
	// and larger number as upper bound
	int lower, upper;
	if (v1 <= v2) {
		lower = v1;
		upper = v2;
	} else {
		lower = v2;
		upper = v1;
	}
	int sum = 0;
	// sum values from lower up to and including upper
	for (int val = lower; val <= upper; ++val)
		sum += val; // sum = sum + val

	std::cout << "Sum of " << lower
		<< " to " << upper
		<< " inclusive is "
		<< sum << std::endl;
	return 0;
}

仅计算一次输入值，未求和

Exercise 1.15:用两个相等的值作为输入编译并运行本节中的程序。将实际输出与你在上一习题中所做的预测相比较，解释实际结果和你预计的结果间的不相符之处。

仅计算一次输入值，未求和

Exercise 1.16:编写程序，输出用户输入的两个数中的较大者。

#include <iostream>
int main()
{
	std::cout << "Enter two numbers:" << std::endl;
	int v1, v2;
	std::cin >> v1 >> v2; // read input
	if (v1 < v2) {
		std::cout<<v2;
	} else if(v1>v2) {
		std::cout<<v1;
	}else{std::cout<<"Two number are equal.";}
	return 0;
}

Exercise 1.17:编写程序，要求用户输入一组数。输出信息说明其中有多少个负数

#include <iostream>
int main()
{
	std::cout << "Enter two numbers:" << std::endl;
	int v1, v2,cout;
	cout = 0;
	std::cin >> v1 >> v2; // read input
	if (v1 < 0) {
		++cout;
	} else if(v2 < 0) {
		++cout;
	}
	std::cout<<cout;
	return 0;
}