C++编程思想第二章习题2_2

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概述

习题2-1

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

void main( void )
{
    string name( "Damon" ); //第一种初始化方式
     int age = 98 ; //第二种初始化方式
    cout<< "name is " <<name<<endl;
    cout<<name<< "'s age is" <<age<<endl;
    system( "pause" );
}

2-2

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#include <iostream>
#include <string>
using namespace std;
const double PI = 3 . 1415926 ; //常量代替宏
void main( void )
{
      int r;
     std::cout<< "Please input the R " <<endl;
     std::cin>>r;
     cout<< "the area of circle is " <<r*r*PI<<endl;
     system( "pause" );
}

2-3

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

void main( void )
{
    string str;
     static int num = 0 ;
    ifstream in( "file.txt" ); //打开文件可读
    getline(in,str); //把文件读到string对象中,有利于对字符串的操作
     for ( int i = 0 ;i<str.size();i++) //用string类的函数
    {
         if (str[i]== ' ' )
        {
            ++num; //空个数，单词数比空格多一个
        }


    }
    cout<<num+ 1 <<endl;

    system( "pause" );

}

2-5

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

void main( void )
{
    string str;
    string dstr( "you" );
     int num = 0 ;
    ifstream in( "file.txt" ); //打开文件可读
    getline(in,str); //把文件读到string对象中,有利于对字符串的操作
     for ( int i = 0 ;i<str.size();i++) //用string类的函数
    {
        cout<<str[str.size()- 1 -i]<<endl;

    }
    system( "pause" );

}

2-5

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

void main( void )
{
    vector<string> words;
    string word;
    ifstream in( "file.txt" );
     while (in>>word) //>> 是定向输入， >>前面是源，后面是目标in>>word就是将in的内容读取到word内
    {
        words.push_back(word); //存入到vector中
    }
     for ( int i = 0 ;i<words.size();i++)
    {
        cout<<words[words.size()- 1 -i]; //逆向输出
    }
    system( "pause" );

}

2-6

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

void main( void )
{
    vector<string> words;
    string word;
    string line;
    ifstream in( "file.txt" );
     while (in>>word)
    {
        words.push_back(word);
    }
     for ( int i = 0 ;i<words.size();i++)
    {
        line += words[i];
    }
    cout<<line;
    system( "pause" );

}

2-8

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#include <iostream>
#include <string>
#include <fstream>
#include <vector>
using namespace std;
const int _INPUT_NUM = 10 ;
void main( void )
{
    vector< float > myArray; //定义浮点型容器
     float j;
     for ( int i = 0 ; i < _INPUT_NUM; i++)
    {
         int k = i + 1 ;
         float num;
        cout << "please input the " << k << "number:" << endl;
        cin >> num;
        myArray.push_back(num); //将元素放入容器
    }
     for ( int j = 0 ; j < myArray.size(); j++)
    {
        cout << myArray[j] << "  " ;

    }
    system( "pause" );

}

2-9

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

const int _INPUT_NUM = 3 ;
void main( void )
{
    vector< float > myArray1; //定义浮点型容器
    vector< float > myArray2; //定义浮点型容器
    vector< float > myArray3; //定义浮点型容器
     for ( int i= 0 ;i<_INPUT_NUM;i++)
    {
         int k = i+ 1 ;
         float num;
        cout<< "please input myArray1 the " <<k<< "number:" <<endl;
        cin>>num;
        myArray1.push_back(num); //将元素放入容器
    }
     for ( int i= 0 ;i<_INPUT_NUM;i++)
    {
         int k = i+ 1 ;
         float num;
        cout<< "please input the myArray1 " <<k<< "number:" <<endl;
        cin>>num;
        myArray2.push_back(num); //将元素放入容器
    }
     int myArray2_size = myArray2.size();
     //主要算法实现把两个容器归到myArray1中
     for ( int i = 0 ;i<myArray2_size;i++)
    {
        myArray1.push_back(myArray2[i]);
    }
    myArray3 = myArray1;
     for ( int i = 0 ;i<myArray3.size();i++)
    {
        cout<<myArray3[i]<<endl;
    }
    system( "pause" );

}

2-10

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//#include<stdafx.h>
#include <algorithm>
#include <iostream>
#include <string>
#include <fstream>
#include <vector>
using namespace std;
const int _INPUT_NUM = 3 ;
void main( void )
{
    vector< float > myArray1; //定义浮点型容器
     for ( int i= 0 ;i<_INPUT_NUM;i++)
    {
         int k = i+ 1 ;
         float num;
        cout<< "please input myArray1 the " <<k<< "number:" <<endl;
        cin>>num;
        myArray1.push_back(num*num); //将元素放入容器
    }
     for ( int i = 0 ;i<myArray1.size();i++)
    {
        cout<<myArray1[i]<<endl;
    }

    system( "pause" );

}