第一章的友好度还是相当滴
习题解答
1.2习题
1.2认为最大的收获：
注意
// Exercise 1.3 Output Hello, World。
#include<iostream>
int main(){
std::cout<< "Hello，World。" << std::endl;
return 0;
}
// Exercise 1.4 Input two numbers by using the char of "*" to print product
#include<iostream>
int main(){
int v1 = 0, v2 = 0;
std::cin >> v1 >> v2;
std::cout << v1 * v2 << std::endl;
return 0;
}
// 将样例输出语句分离单个语句中
// std::out<<"The sum of: "<<v1 + v2<<" end!"<<std::endl
#include<iostream>
int main(){
int v1 = 5, v2 = 3;
std::cout << "The sum of: ";
std::cout << v1 + v2;
std::cout << " end!";
std::cout << std::endl;
return 0;
}
1.4习题~(循环与不定量数据读入)
// use "while" sum 50 + 51 + 52 .... + 100 print reult
#include<iostream>
int main(){
int val = 50, sum = 0;
while(val <= 100){
sum += val;
val++;
}
std::cout << sum;
return 0;
}
// use "while" print 10 9 8 ... 0
#include<iostream>
int main(){
int val = 10;
while(val >= 0){
std::cout << val << " ";
val--;
}
std::cout << std::endl;
return 0;
}
// 编写程序输入两个整数 打印这两个整数范围内的所有整数
#include<iostream>
int main(){
int left = 0, right = 0;
std::cin >> left >> right;
std::cout << "[left, right] includes: ";
while(left <= right){
std::cout << left << " ";
left++;
}
std::cout << std::endl;
return 0;
}
// use "for" sum of 50~100
#include<iostream>
int main(){
int sum = 0;
for(int i = 50; i <= 100; i++){
sum += i;
}
std::cout << "Sum of : " << sum << std::endl;
return 0;
}
// print 10 to 0 use "for" and "--"
#include<iostream>
int main(){
for(int i = 10; i >= 0; --i){
std::cout << i << " ";
}
std::cout << std::endl;
return 0;
}
// input two numbers [a, b] print a to b all numbers
#include<iostream>
int main(){
int a = 0, b = 0;
std::cin >> a >> b;
for(int i = a; i <= b; i++){
std::cout << i << " ";
}
std::cout << std::endl;
return 0;
}
// 从cin 读取一组数 求和 不定量数据
#include<iostream>
int main(){
int val = 0, sum = 0;
while(std::cin >> val){
sum += val;
}
std::cout << "sum of " << sum << std::endl;
return 0;
}
最后~简单的C++项目 书店程序
收获：类的初次了解，c++项目的创建与操作 以下要点(附书中头文件源码)
注意
由于项目的设计，以下将练习封装为函数以便区分
#include"Sales_item.h"
void readAndPrint();
void testAdd();
void sumOfSales();
void staSales();
void completeRoutine();
int main(void) {
//readAndPrint();
//testAdd();
//sumOfSales();
//staSales();
completeRoutine();
return 0;
}
// p20 1.5.1_1 读取一组图书销售记录 并且将记录打印在标准输出
void readAndPrint(){
Sales_item book;
std::cin >> book;
std::cout << book << std::endl;
}
// 1.5.1_2 读取两个ISBN(书号)相同的Sales_item 对象, 输出和
void testAdd(){
Sales_item item1, item2;
std::cout << "输入两个相同ISBN的书籍信息 (书号 售出本数 单价)" << std::endl;
std::cin >> item1 >> item2;
std::cout << item1 + item2 << std::endl;
}
// 1.5.1_3 读取具有多个连续相同ISBN的记录 输出所有相同记录的和
void sumOfSales(){
std::cout << "输入多个相同ISBN的书籍信息 (书号 售出本数 单价)" << std::endl;
Sales_item item, sum;
while(std::cin >> item){// ctrl+z 录入结束
sum += item;
}
std::cout << "sum of " << sum << std::endl;
}
// p21 1.5.2_1 读取多条销售记录 并统计每个ISBN(即每本书)有几条记录
void staSales(){
std::cout << "输入多条书籍销售记录 (书号 售出本数 单价)" << std::endl;
Sales_item curItem, nextItem;
if(std::cin >> curItem){
int cnt = 1; // 记录条数
while(std::cin >> nextItem){
if(nextItem.isbn == curItem.isbn){
cnt++;
}else{
std::cout << curItem.isbn << " has saled " << cnt << " books"<<std::endl;
curItem = nextItem;
cnt = 1; // 初始化计数
}
}
// 打印最后一条记录
std::cout << curItem.isbn << " has saled " << cnt << " books"<<std::endl;
}
}
// 书店程序
// 假定读入的销售记录书号相同的已经聚在一起 输出每本书的最终销售记录
void completeRoutine(){
std::cout << "输入多条书籍销售记录 (书号 售出本数 单价)" << std::endl;
Sales_item curItem, nextItem;
if(std::cin >> curItem){
while(std::cin >> nextItem){
if(nextItem.isbn == curItem.isbn){
curItem += nextItem;// 销售信息累加
}else{
std::cout << "销售记录：" << curItem << std::endl;
curItem = nextItem;// 更新为下一本数的销售情况
}
}
// 最后一本书的记录
std::cout << "销售记录：" << curItem << std::endl;
}else{
std::cout << "无效的书籍信息!" << std::endl;
}
}
以上引用头文件源码
#ifndef SALESITEM_H
#define SALESITEM_H
#include <iostream>
#include <string>
class Sales_item{
public:
Sales_item(const std::string &book):isbn(book),units_sold(0),revenue(0.0){}
Sales_item(std::istream &is){ is >> *this;}
friend std::istream& operator>>(std::istream &,Sales_item &);
friend std::ostream& operator<<(std::ostream &,const Sales_item &);
public:
Sales_item & operator+=(const Sales_item&);
public:
double avg_price() const;
bool same_isbn(const Sales_item &rhs)const{
return isbn == rhs.isbn;
}
Sales_item():units_sold(0),revenue(0.0){}
public:
std::string isbn;
unsigned units_sold;
double revenue;
};
using std::istream;
using std::ostream;
Sales_item operator+(const Sales_item &,const Sales_item &);
inline bool operator==(const Sales_item &lhs,const Sales_item &rhs){
return lhs.units_sold == rhs.units_sold && lhs.revenue == rhs.revenue && lhs.same_isbn(rhs);
}
inline bool operator!=(const Sales_item &lhs,const Sales_item &rhs){
return !(lhs == rhs);
}
inline Sales_item & Sales_item::operator +=(const Sales_item &rhs){
units_sold += rhs.units_sold;
revenue += rhs.revenue;
return *this;
}
inline Sales_item operator+(const Sales_item &lhs,const Sales_item &rhs){
Sales_item ret(lhs);
ret += rhs;
return ret;
}
inline istream& operator>>(istream &in,Sales_item &s){
double price;
in >> s.isbn >> s.units_sold >> price;
if(in)
s.revenue = s.units_sold * price;
else
s = Sales_item();
return in;
}
inline ostream& operator<<(ostream &out,const Sales_item &s){
out << s.isbn << "\t" <<s.units_sold << "\t" << s.revenue << "\t" << s.avg_price();
return out;
}
inline double Sales_item::avg_price() const{
if(units_sold)
return revenue/units_sold;
else
return 0;
}
#endif
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