c++primer4 Chapter1

Exercise1.17

#include <iostream>

 

int main()

{

  int limit = 0, k = 0, value = 0;

  std::cout << "How many integers would you like to enter?";

  std::cin >> limit;

 

  // assume we don't know what is EOF(End-Of-File).

  while (std::cin >> value && (--limit != 0))

    if (value<0) {

                   k++;

         }

  std::cout << "the number of negative values is " << k<<std::endl;

 

  return 0;

}

 

Exercise1.18

#include <iostream>

using namespace std;

int main()

{

  cout<<"Enter two numbers:";

  int v1,v2;

  cin>>v1>>v2;

  int lower,upper;

  if (v1>=v2) {

           upper=v1;lower=v2;

  }

  else { upper=v2;lower=v1;

  }

  cout<<"Value of "<<lower<<" to "<<upper<<" inclusive are: "<<endl;

  for (int value=lower;value<=upper;value++)

           cout<<value<<" ";

  return 0;

}

Exercise1.19

#include <iostream>
using namespace std;
int main()
{
cout<<"Enter two numbers:";
int v1,v2;
cin>>v1>>v2;
int lower,upper;
if (v1>=v2) {
upper=v1;lower=v2;
}
else { upper=v2;lower=v1;
}
cout<<"Value of "<<lower<<" to "<<upper<<" inclusive are: "<<endl;
for (int value=lower,count=1;value<=upper;value++,count++) {
cout<<value<<" ";
if (count%10==0)
cout<<endl;
}
return 0;
}

添加的变量count是为了记录已输出数的个数，若count的值是10的整数倍，则输出一个换行符。