《C++编程思想》（第二版）第2章 对象的创建和使用（习题及答案）

标签：c++   vector   

与习题相关的代码

Hello.cpp

<span style="font-size:18px;">#include <iostream>
using namespace std;
 
int main()
{
	 cout << "Hello, World! I am " 
    << 8 << " Today!" << endl;
}</span>

Stream2.cpp

<span style="font-size:18px;">#include <iostream>
using namespace std;
 
int main()
{
	cout<<"a number in decimal:"
		<<dec<<15<<endl;
	cout<<"in octal:"<<oct<<15<<endl;
	cout<<"in hex:"<<hex<<15<<endl;
	cout<<"a floatint-point number:"
		<<3.14159<<endl;
	cout<<"non-printing char (escape):"
		<<char(27)<<endl;
	return 0;
}</span>

Nomconv.cpp

<span style="font-size:18px;">#include <iostream>
using namespace std;
 
int main()
{
	int number;
	cout<<"Enter a decimal number:";
	cin>>number;
	cout<<"value in octal = 0"
		<<oct<<number<<endl;
	cout<<"value in hex = 0x"
		<<hex<<number<<endl;
	return 0;
}</span>

Fillvector.cpp

<span style="font-size:18px;">#include <iostream>
#include <fstream>
#include <vector>
using namespace std;
 
int main()
{
	vector<string> v;
	ifstream in("Fillvector.cpp");
	string line;
	while(getline(in,line))
	{
		v.push_back(line);
	}
	for(int i = 0;i < v.size();++i)
	{
		cout<<i<<":"<<v[i]<<endl;
	}
	return 0;
}</span>

2-1修改Hello.cpp，使他打印你的名字和年龄（或者你的鞋码、爱犬的年龄等，只要你喜欢）。编译并运行修改后的程序。

<span style="font-size:18px;">#include <iostream>
using namespace std;

int main() 
{
  cout << "Hello, World! I am ZY." << endl;
  cout << "I am 19 years:" << endl;
  return 0;
}</span>

2-2以Stream.cpp、Numconv.cpp为例，编一个程序，让它根据输入的半径值求出圆面积并打印。可以用运算符“*”求直径的平方。注意，不要用八进制或十六进制格式打印（它们只适用整数类型）。

#include <iostream>
using namespace std;

int main() 
{
  const float pi = 3.141592654;
  cout << "Enter the radius: ";
  
  float radius;
  cin >> radius;
  cout << "The area is " << pi * radius * radius << endl;

  return 0;
}

2-3编一个程序用来打开文件并统计文件中以空格隔开的单词数目。

#include <string>
#include <iostream>
#include <fstream>
#include <string>
using namespace std;

int main() 
{
  ifstream f("test.cpp");
  int nwords = 0;
  string word;

  while (f >> word)
  {
    ++nwords;
  }

  cout << "Number of words = " << nwords << endl;

  return 0;
}

2-4编一个程序统计文件中特定单词出现的次数（要求使用string类的运算符“==”来查找单词）。

#include <iostream>
#include <fstream>
#include <string>
using namespace std;

int main(int argc, char* argv[]) 
{
  // Process command-line arguments:
  if (argc < 3) 
  {
    cerr << "usage: WordCount word file\n";
    return -1;
  }
  string word(argv[1]);
  ifstream file(argv[2]);

  // Count occurrences:
  long wcount = 0;
  string token;
  while (file >> token)
    if (word == token)
      ++wcount;

  // Print result:
  cout << '"' << word << "\" appeared "
       << wcount << " times\n";
} 

2-5修改Fillvector.cpp是他从后向前打印各行。

方法一：

#include <string>
#include <iostream>
#include <fstream>
#include <vector>
using namespace std;

int main() 
{
  vector<string> v;
  ifstream in("Fillvector.cpp");
  string line;
  while(getline(in, line))
  {
    v.push_back(line);
  }

  // Print backwards:
  for(int i = v.size()-1; i > 0; --i) 
  {
    cout << v.size()-1 << ": " << v[i] << endl;
  }
  return 0;
} 

方法二：

#include <string>
#include <iostream>
#include <fstream>
#include <vector>
using namespace std;

int main() 
{
  vector<string> v;
  ifstream in("Fillvector.cpp"<span style="font-family: Arial, Helvetica, sans-serif;">);</span>
  string line;
  while(getline(in, line))
    v.push_back(line);

  // Print backwards:
  int nlines = v.size();
  for(int i = 0; i < nlines; i++) 
  {
    int lineno = nlines-i-1;
    cout << lineno << ": " << v[lineno] << endl;
  }
  return 0;
} 

2-6修改Fillvector.cpp使他把vector中的所有元素连接成单独的一个字符串，并打印，但不要加上行号。

#include <string>
#include <iostream>
#include <fstream>
#include <vector>
using namespace std;

int main() 
{
  vector<string> v;
  ifstream in("Fillvector.cpp");
  string line;
  while(getline(in, line))
  {
    v.push_back(line);
  }
  // Put lines into a single string:
  string lines;
  for(int i = 0; i < v.size(); i++)
  {
    lines += v[i] + "\n";
  }
  cout << lines;
  return 0;
} 

2-7编一个程序，一次显示文件的一行，然后，等待用户按回车键后显示下一行。

#include <string>
#include <iostream>
#include <fstream>
using namespace std;

int main() 
{
  ifstream in("test.cpp");
  string line;
  while(getline(in, line)) 
  {
    cout << line;  // No endl!
    cin.get();
  }

  return 0;
}

2-8创建一个vector<float>，并用一个for循环语句向它输入25个浮点数，显示vector的结果。

#include <iostream>
#include <vector>
using namespace std;

int main() 
{
  // Fill vector:
  vector<float> v;
  for (int i = 0; i < 25; ++i)
  {
    v.push_back(i + 0.5);
  }

  // Display
  for (int i = 0; i < v.size(); ++i) 
  {
	  cout << v[i]<<" ";
  }
  cout << endl;

  return 0;
}

2-9创建三个vector<float>对象，与第八题一样填写前两个对象。编一个for循环，把前两个vector的每一个对应的元素相加起来，结果放入第三个vector的相应元素中。显示这三个vector的结果。

方法一：

#include <iostream>
#include <vector>
using namespace std;

int main()
{
  vector<float> v1, v2;
  for (int i = 0; i < 25; ++i) 
  {
    v1.push_back(i);
    v2.push_back(i + 0.2);
  }

  // Form sum:
  vector<float> v3;
  for (int i = 0; i < v1.size(); ++i)
  {
    v3.push_back(v1[i] + v2[i]);
  }

  // Display:
  for (int i = 0; i < v1.size(); ++i) 
  {
    cout << v1[i] << " + " << v2[i]
         << " = " << v3[i] << endl;
  }

  return 0;
}

方法二：

#include <iostream>
#include <vector>
using namespace std;

int main()
{
  vector<float> v1, v2;
  for (int i = 0; i < 25; ++i) 
  {
    v1.push_back(i);
    v2.push_back(i + 0.2);
  }

  // Form sum:
  vector<float> v3;
  v3.resize(v1.size());  // pre-allocate space
  for (int i = 0; i < v1.size(); ++i)
  {
    v3[i] = v1[i] + v2[i];
  }

  // Display:
  for (int i = 0; i < v1.size(); ++i) 
  {
    cout << v1[i] << " + " << v2[i]
         << " = " << v3[i] << endl;
  }

  return 0;
}

2-10编一个程序，创建一个vector<float>，像前面的练习那样输入25个数。求每个数的平方，并把它们放入vector的同样位置。显示运算前后的vector。
#include <iostream>
#include <vector>
using namespace std;

int main() 
{
  // Fill and print:
  vector<float> v;
  for (int i = 0; i < 25; ++i)
  {
    v.push_back(i);
  }
  for (int i = 0; i < v.size(); ++i) 
  {
    cout << v[i]<<" ";
  }
  cout<<endl;
  // Square and print:
  for (int i = 0; i < v.size(); ++i)
  {
    v[i] = v[i] * v[i];
  }
  for (int i = 0; i < v.size(); ++i) 
  {
    cout << v[i]<<" ";
  }
  cout<<endl;

  return 0;
}

《C++编程思想》（第二版）第2章 对象的创建和使用（习题及答案）

标签：c++   vector   

原文地址：http://blog.csdn.net/qaz3171210/article/details/47031357