C++编程思想第二章习题2_2

最新推荐文章于 2021-09-14 13:47:59 发布

damon1118

最新推荐文章于 2021-09-14 13:47:59 发布

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分类专栏：课后习题

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本文详细介绍了C++编程的基础知识，包括变量初始化、常量替代宏、文件读写操作、字符串处理、循环和条件语句等核心概念，并通过具体代码示例展示了如何在实际场景中应用这些知识。

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习题2-1

 C++ Code 

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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

 C++ Code 

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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

 C++ Code 

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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

 C++ Code 

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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

 C++ Code 

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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

 C++ Code 

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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

 C++ Code 

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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

 C++ Code 

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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

 C++ Code 

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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");

}