c++primer 学习笔记（1.0）快速入门

第一章 快速入门

一个使用IO库的程序

#include <iostream>
int main()
{
std::cout<<"Enter two numbers:"<<std::endl;
int v1,v2;
std::cin>>v1>>v2;
std::cout<<"The sum of "<<v1<<" and "<<v2<<" is "<<v1+v2<<std::endl;
return 0;
}

Std::cout等等的应用是一个亮点，不用在预处理之后加上using namespace std;d的说明，程序简单的话很好用。

除了cout,还有ceer,clog等输出用法；

另外putchar也可以哦，例如“putchar('a\n')”头文件依旧是#include<iostream>;

Endl可以刷新与设备关联的缓冲区buffer。经常刷新buffer是个好习惯！

习题1.3

打印Hello world!

#include <iostream>
int main()
{
std::cout<<"Hello world !"<<std::endl;
return 0;
}

习题1.4：

求两数之积

#include <iostream>
int main()
{
std::cout<<"Enter two numbers:"<<std::endl;
int v1,v2;
std::cin>>v1>>v2;
std::cout<<"The product of "<<v1<<" and "<<v2<<" is "<<v1*v2<<std::endl;
return 0;
}

习题1.5

使用单独语句打印

#include <iostream>
int main()
{
std::cout<<"Enter two numbers:"<<std::endl;
int v1,v2;
std::cin>>v1>>v2;
std::cout<<"The product of ";
std::cout<<v1;
std::cout<<" and ";
std::cout<<v2;
std::cout<<" is ";
std::cout<<v1*v2;
std::cout<<std::endl;
return 0;
}

1.3关于注释

有两种 单行注释 // 和多行注释/**/

注释不可嵌套！！

注释是忽略一大段代码的好方法，在每一行上加一个//而不是在首尾处加上多行注释（可能有注释嵌套，造成erro）

#include <iostream>
int main()
{
std::cout<<"/*";
std::cout<<"*/";
std::cout<</*"*/"*/";   //小心注释
 
return 0;
}

While语句运用，从1加到n；

#include <iostream>
int main()
{
int sum=0,i,;
std::cout<<"Enter a postive number:"<<std::endl;
std::cin>>i;
int j=i;	 
while(i) {
sum+=i;
i--;
} 
std::cout<<"sum of "<<1<<" to "<<j<<" is "<<sum<<std::endl ;
return 0;
}

For语句的运用，将刚才的程序改变一下：

#include <iostream>
int main()
{
int sum=0,i,;
std::cout<<"Enter a postive number:"<<std::endl;
std::cin>>i;
int j=i;	 
for(;i!=0;i--) {
sum+=i;
} 
std::cout<<"sum of "<<1<<" to "<<j<<" is "<<sum<<std::endl ;
return 0;
}

习题1.10

#include <iostream>
int main()
{
int sum=0;	 
for(int val=50;val!=101;val++) {
sum+=val;
} 
std::cout<<"sum of "<<50<<" to "<<500<<" is "<<sum<<std::endl ;
return 0;
}

用while改变

#include <iostream>
int main()
{
int sum=0,val=50;	 
while(val<=100) {
sum+=val;
val++;
}
std::cout<<"sum of "<<50<<" to "<<500<<" is "<<sum<<std::endl ;
return 0;
}

习题1.11

#include <iostream>
int main()
{
int val=10;	 
while(val>=0) {
std::cout<<val<<std::endl;
val--;
}
return 0;
}

用for循环改编

#include <iostream>
int main()
{
int val=10;	 
for(;val>=0;val--) {
std::cout<<val<<std::endl;
}
return 0;
}

求某两个数的和

If语句

#include <iostream>
using namespace std;
int main()
{
int v1,v2,lower,upper,sum=0;
cout<<"Enter two numbers"<<endl;
cin>>v1>>v2;
if(v1>v2) {
upper=v1;
lower=v2;
}
else {
upper=v2;
lower=v1;
}
for(int val=lower;val<=upper;val++) {
sum+=val;
}
cout<<"The sum between "<<lower<<" and "<<upper<<" is "<<sum<<endl;
return 0;
}

习题1.16

#include <iostream>
using namespace std;
int main()
{
cout<<"enter two numbers to find the bigger one:";
int v1,max;
cin>>v1>>max;
if(v1>max) {
max=v1;
}
cout<<"the bigger one is "<<max<<endl;
return 0;
}

习题1.17

#include <iostream>
using namespace std;
int main()
{
cout<<"enter lots of numbers to find how many positive numbers in them:"<<endl<<"press ctrl+z to stop entering"<<endl;
int val,count=0;
while(cin>>val)
if(val>0) count++;
cout<<"There are "<<count<<" positive numbers in them."<<endl;
return 0;
}

读入未知数目数字求和

#include <iostream>
using namespace std;
int main()
{
cout<<"enter lots of numbers to calculate the sum of them:"<<endl<<"press ctrl+z to stop entering"<<endl;
int val,sum=0;
while(cin>>val)
if(val>0){
sum+=val;
}
cout<<"The sum of them is"<<sum<<endl;
return 0;
}

习题1.18

#include <iostream>
using namespace std;
int main()
{
cout<<"enter two numbers :"<<endl;
int v1,v2,upper,lower;
cin>>v1>>v2;
if(v1>v2) {
upper=v1;
lower=v2;
}
else {
upper=v2;
lower=v1;
}
int val;
    for(val=lower;val<=upper;val++)
    cout<<val<<endl;
return 0;
}

习题1.19

#include <iostream>
#include <iomanip>
using namespace std;
int main()
{
cout<<"enter two numbers :"<<endl;
int v1,v2,upper,lower;
cin>>v1>>v2;
if(v1>v2) {
upper=v1;
lower=v2;
}
else {
upper=v2;
lower=v1;
}
int val,amount=0;
    for(val=lower;val<=upper;val++) {
    	    cout<<setw(2)<<val<<" ";
amount++;
if(amount==10) {
    	cout<<endl;
    	amount=0;
    }
    }
    
return 0;
}

习题1.20

#include <iostream>
using namespace std;
int main()
{
int v1,v2,amount,sum=0;
cout<<"Enter two numbers"<<endl;
cin>>v1>>v2;
amount=v1-v2;
if(amount<0) amount=-amount+1;
else amount+=1; 
sum=(v1+v2)*(amount)/2;
cout<<"The sum between "<<v1<<" and "<<v2<<" is "<<sum<<endl;
return 0;
}

类

标准库的头文件用<>；非标准库的头文件用""

如

#include <iostream>
#include"Sales_item.h" 
using namespace std;
int main()
{
   Sales_item item1,item2;
   cin>>item1>>item2;
   cout<<item1+item2<<endl;
   return 0;  
}

习题1.21

#include <iostream>
#include"Sales_item.h" 
using namespace std;
int main()
{
   Sales_item book;
   while(cin>>book) {
   	cout<<"ISBN,numbers of copies sold,total revenur,and average price are:"
   	<<endl<<book<<endl;
   }
    return 0; 
}

习题1.22

#include <iostream>
#include"Sales_item.h" 
using namespace std;
int main()
{
   Sales_item item1,item2,item;
   cout<<"Enter two objects:\n";
   cin>>item1>>item2;
   if(item1.same_isbn(item2))
   	cout<<"ISBN,numbers of copies sold,total revenur,and average price are:"
   	<<endl<<item1+item2<<endl;
   	else 
   	cout<<"The two objects have different ISBN"<<endl;
    return 0; 
}

习题1.23

#include <iostream>
#include"Sales_item.h" 
using namespace std;
int main()
{
   Sales_item item,book;
   cout<<"Enter many objects:\n";
   cin>>book;
   while(cin>>item)
   if(book.same_isbn(item)) {
   book+=item;
   }   
   	else {
   	  	cout<<"The objects have different ISBN"<<endl;
        return -1;
   }
   	cout<<"ISBN,numbers of copies sold,total revenur,and average price are:"
   	<<endl<<book<<endl;
    return 0; 
}

习题1.24

#include <iostream>
#include"Sales_item.h" 
using namespace std;
int main()
{
   Sales_item item1,item2;
   int amount=1;
   cout<<"Enter many objects:\n";
   cin>>item1;//读入第一笔交易，即初始交易。 
   while(cin>>item2)
   if(item1.same_isbn(item2)) {
   ++amount;
   } 
   //ISBN不同时首先计算之前ISBN的总和，然后再将amount赋值为1  
   	else {
  	    cout<<"transaction amount of previous ISBN:"
   	<<endl<<amount<<endl;
   	   amount=1;
   	   item1=item2;   	   
   } 
    cout<<"transaction amount of the last ISBN :"<<amount<<endl;
    return 0; 
}

习题1.25

#include <iostream>
#include"Sales_item.h" 
using namespace std;
int main()
{
   Sales_item total,trans;
   cout<<"Enter some objects:\n(press ctrl+z to stop entering)\n";
   if(cin>>total) {
   while(cin>>trans)
   if(total.same_isbn(trans))
     total+=trans;
   else {
   	cout<<"transaction of previous :"<<total<<endl;
    total=trans;
   }  
   }
   else {
   	cout<<"no input!  no data!"<<endl; 
    return -1;
   }  
    return 0; 
}