c++ primer中文版第五版作业第一章

1.1

int main()
{return 0;
}

1.2

int main()
{return -1;
}

1.3

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

1.4

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

1.5

#include <iostream>
int main()
{std::cout<<"Enter two numbers:";std::cout<<std::endl;int v1=0,v2=0;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;
}

1.6

 不合法，因为第二三行缺乏输出运算符的左侧运算对象。
应该修改为：
std::cout<<"The sum of “<<v1;
std::cout<<” and “<<v2;
std::cout<<” is "<<v1+v2<<std::endl;

1.7

#include <iostream>
int main()
{std::cout<<"Enter two numbers:";std::cout<<std::endl;/*这是一个嵌套注释的程序* 我们来看看/**/*编译后*的错误提示*/int v1=0,v2=0;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;
}

1.8

#include <iostream>
int main()
{//只有第三行的错误的std::cout<<"/*";std::cout<<"*/";//std::cout<</*"*/"*/;std::cout<</**/"*/";//上一行的更正std::cout<</* "*/" /* "/*"  */;return 0;
}

1.9

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

1.10

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

1.11

#include <iostream>
int main()
{int val1,val2,tmp;std::cout<<"Enter two integer:";std::cin>>val1>>val2;if(val1<val2){tmp=val1;val1=val2;val2=tmp;}std::cout<<"Print total numbers in the range from "<<val1<<" to "<<val2<<std::endl;while(val1>=val2){std::cout<<val1<<" ";val1--;}std::cout<<std::endl;return 0;
}

1.12

 for循环完成从-100累加到100，sum的终值是0。
###1.13

#include <iostream>
int main()
{for(int val=10;val>=0;val--)std::cout<<val<<std::endl;return 0;
}
#include <iostream>
int main()
{int val1,val2,tmp;std::cout<<"Enter two integer:";std::cin>>val1>>val2;if(val1<val2){tmp=val1;val1=val2;val2=tmp;}std::cout<<"Print total numbers in the range from "<<val1<<" to "<<val2<<std::endl;for(;val1>=val2;val1--)std::cout<<val1<<" ";std::cout<<std::endl;return 0;
}
#include <iostream>
int main()
{int sum=0;for(int val=50;val<=100;val++)sum+=val;std::cout<<"Sum of 50 to 100 inclusive is "<<sum<<std::endl;return 0;
}

1.14

 while 循环的 优点 是书写简单，缺点 是程序员可能忘记在循环体（statement）内作用条件判断语句（condition），造成无限循环；for 循环的 优点 是规范、整洁，不易漏掉作用条件判断（condition）的表达式（expression），缺点 是书写稍繁琐。while 循环适合循环次数不确定的情景；for 循环适合循环次数事先已知。

1.15

#include <iostream>
int main()
{std::cout<<"Read each file."<<std::endl:std::cout<< Update master. <<std::endl;std::cout<<"Write new master." std::endl;return 0
}

1.16

#include <iostream>
int main()
{int sum=0,value=0;while(std::cin>>value)sum+=value;std::cout<<"The sum is "<<sum<<"."<<std::endl;return 0;
}

1.17

 如果输入的所有值都相等，本节程序会输出该值出现多少次。如果没有重复值，输出会是每个值出现一次。

1.18

• 所有值都相等
  1 1 1 1 1
  1 occurs 5 time.
• 没有重复值
  1 2 3
  1 occurs 1 times.
  2 occurs 1 times.
  3 occurs 1 time.

1.19

#include <iostream>
int main()
{int val1,val2,tmp;std::cout<<"Enter two integer:";std::cin>>val1>>val2;if(val1<val2)//处理用户输入的第一个数比第二个数小的情况{tmp=val1;val1=val2;val2=tmp;}std::cout<<"Print total numbers in the range from "<<val1<<" to "<<val2<<std::endl;while(val1>=val2){std::cout<<val1<<" ";val1--;}std::cout<<std::endl;return 0;
}

1.20

#include <iostream>
#include "Sales_item.h"
int main()
{Sales_item tmp;while(std::cin>>tmp)std::cout<<tmp<<std::endl;return 0;
}

1.21

#include <iostream>
#include "Sales_item.h"
int main()
{Sales_item result,tmp;std::cin>>result>>tmp;std::cout<<result+tmp<<std::endl;return 0;
}

1.22

#include <iostream>
#include "Sales_item.h"
int main()
{Sales_item result,tmp;std::cin>>result;while(std::cin>>tmp)result+=tmp;std::cout<<result<<std::endl;return 0;
}

1.23

#include <iostream>
#include "Sales_item.h"
int main()
{Sales_item current_item,next_item;if(std::cin>>current_item){int cnt=1;while(std::cin>>next_item){if(current_item.isbn()==next_item.isbn()){current_item+=next_item;cnt++;}else{std::cout<<current_item<<" ocurrs "<<cnt<<" times."<<std::endl;current_item=next_item;cnt=1;}}std::cout<<current_item<<" ocurrs "<<cnt<<" times."<<std::endl;}return 0;
}

1.24

运行结果:

0-201-78345-X 4 25.0
0-201-78345-X 1 25.0
0-201-78345-X 2 25.0
0-201-78345-X 9 25.0
0-207-78345-X 9 31.0
0-207-78345-X 3 31.0
0-202-78345-X 3 20.0
0-202-78345-X 3 20.0

1.25

#include <iostream>
#include "Sales_item.h"
int main()
{Sales_item total;if(std::cin>>total){Sales_item trans;while(std::cin>>trans){if(total.isbn()==trans.isbn())total+=trans;else{std::cout<<total<<std::endl;total=trans;}}std::cout<<total<<std::endl;}else{std::cerr<<"No data?"<<std::endl;return -1;}return 0;
}

运行结果:

0-201-78345-X 16 400 25
0-207-78345-X 12 372 31
0-202-78345-X 6 120 20