C++ Primer Plus第六版第六章分支语句和逻辑运算符编程练习答案
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1.
#include<iostream>
#include<cctype>
using namespace std;
int main()
{
char ch;
while (cin.get(ch) && ch != '@')
{
if (isupper(ch))
{
ch = tolower(ch);
cout << ch;
}
else if (islower(ch))
{
ch = toupper(ch);
cout << ch;
}
}
return 0;
}
2.
#include<iostream>
using namespace std;
int main()
{
double sum = 0, ave = 0;
int m = 0, i = 0;
double donation[10];
while (i < 10 && (cin >> donation[i]))
sum += donation[i++];
if (i == 0)
cout << "输入有误" << endl;
else
ave = sum / i;
for (int j = 0; j < i; ++j)
if (donation[j] > ave)
++m;
cout << "这些数字的平均值是: " << ave << endl;
cout << "有" << m << "个数字大于平均值" << endl;
return 0;
}
3.
#include<iostream>
using namespace std;
int main()
{
cout << "Please enter one of the following choices:" << endl;
cout << "c) carnivore p) pianist" << endl;
cout << "t) tree g) game" << endl;
char ch;
while (cin >> ch)
{
switch(ch)
{
case 'c':
cout << "A tiger is a carnivore.";
return 0;
case 'p':
cout << "lang lang is a pianist.";
return 0;
case 't':
cout << "A maple is a tree.";
return 0;
case 'g':
cout << "lol is a game.";
return 0;
default :
cout << "Please enter a c, p, t, or g: ";
break;
}
}
}
4.
#include<iostream>
using namespace std;
const int strsize = 20;
struct bop {
char fullname[strsize];
char title[strsize];
char bopname[strsize];
int preference;
};
int main()
{
bop data[5] = {
{"Wimp Macho", "Student", "Macho", 0},
{"Raki Rhodes", "Junior Programmer", "Rhodes", 1},
{"Celia Laiter", "Student", "MIPS", 2},
{"Hoppy Hipman", "Analyst Trainee", "Hipman", 1},
{"Pat Hand", "Student", "LOOPY", 2}
};
cout << "Benevolent Order of Programmers Report\n";
cout << "a. display by name b. display by title\n";
cout << "c. display by bopname d. display by preference\n";
cout << "q. quit" << endl;
cout << "Enter your choice: ";
char choice;
while (cin >> choice)
{
switch (choice)
{
case 'a':
for (int i = 0; i < 5; ++i)
cout << data[i].fullname << endl;
break;
case 'b':
for (int i = 0; i < 5; ++i)
cout << data[i].title << endl;
break;
case 'c':
for (int i = 0; i < 5; ++i)
cout << data[i].bopname << endl;
break;
case 'd':
for (int i = 0; i < 5; ++i)
{
if (data[i].preference == 0)
cout << data[i].fullname << endl;
else if (data[i].preference == 1)
cout << data[i].title << endl;
else
cout << data[i].bopname << endl;
}
break;
case 'q':
cout << "Bye!";
return 0;
default:
cout << "Please enter a, b, c, d or q: ";
break;
}
}
}
5.
#include<iostream>
using namespace std;
const int strsize = 20;
int main()
{
int n;
cout << "输入你的收入: ";
while ((cin >> n) && n >= 0)
{
if (n <= 5000)
cout << "不用交税\n";
else if (n <= 15000)
cout << "需要交税:" << (15000 - n) * 0.1 << endl;
else if (n <= 35000)
cout << "需要交税:" << 10000 * 0.10 + (n - 15000) * 0.15 << endl;
else
cout << "需要交税:" << 10000 * 0.10 + 20000 * 0.15 + (n - 35000) * 0.20 << endl;
cout << "输入另一个收入(输入字母或负数结束): ";
}
cout << "程序结束！" << endl;
return 0;
}
6.
#include<iostream>
#include <string>
using namespace std;
struct data {
string name;
double amount;
};
int main()
{
int n;
cout << "请输入捐献者数目: ";
while (!(cin >> n) || n < 0)
{
cin.clear();//重置错误输入标记,程序才能继续读取输入
while (cin.get() != '\n')//读取行尾之前的所有输入，删除一行的错误输入
continue;
cout << "输入错误，请重新输入: ";
}
if (n == 0)
{
cout << "没有捐献者，程序结束!" << endl;
return 0;
}
cin.get();
struct data *pf = new struct data[n];
for (int i = 0; i < n; ++i)
{
cout << "输入第" << i + 1 << "个捐献者的姓名: ";
getline(cin, pf[i].name);
cout << "输入第" << i + 1 << "个捐献者捐献的金额: ";
while (!(cin >> pf[i].amount) || n < 0)
{
cin.clear();//重置错误输入标记,程序才能继续读取输入
while (cin.get() != '\n')//读取行尾之前的所有输入，删除一行的错误输入
continue;
cout << "输入错误，请重新输入: ";
}
cin.get();
}
cout << "重要捐款人:\n";
int temp = 0;
for (int i = 0; i < n; ++i)
if (pf[i].amount > 10000)
{
cout << pf[i].name << endl;
++temp;
}
if (temp == 0)
cout << "none" << endl;
temp = 0;
cout << "其他捐献人:\n";
for (int i = 0; i < n; ++i)
if (pf[i].amount <= 10000)
{
cout << pf[i].name << endl;
++temp;
}
if (temp == 0)
cout << "none" << endl;
delete []pf;
return 0;
}
7.
#include<iostream>
#include<cctype>
#include<cstring>
#include<string>
using namespace std;
int main()
{
string s;
int vowels = 0, consonants = 0, others = 0;
cout << "Enter words (q to quit):\n";
while (cin >> s && (s != "q"))
{
if (isalpha(s[0]))
{
if (strchr("aeiou", s[0]))
++vowels;
else
++consonants;
}
else
++others;
}
cout << vowels << " words beginning with vowels\n";
cout << consonants << " words beginning with consonants\n";
cout << others << " others" << endl;
return 0;
}
8.
#include<iostream>
#include<fstream>
#include<cstdlib>
const int SIZE = 60;
using namespace std;
int main()
{
char filename[SIZE];
ifstream inFile;
cout << "输入你想要打开的文件名(如xx.txt):" << endl;
cin.getline(filename, SIZE);
inFile.open(filename);
if (!inFile.is_open())
{
cout << "无法打开文件，可能文件不存在或者路径不对";
exit(EXIT_FAILURE);
}
char ch;
int num = 0;
while (inFile >> ch)
++num;
cout << "该文件一共有" << num << "个字符." << endl;
inFile.close();
return 0;
}
9.
#include<iostream>
#include<fstream>
#include<cstdlib>
using namespace std;
const int SIZE = 60;
struct data {
char name[SIZE];
double amount;
};
int main()
{
int n;
char filename[SIZE];
ifstream inFile;
cout << "输入你想要打开的文件名(如xx.txt):" << endl;
cin.getline(filename, SIZE);
inFile.open(filename);
if (!inFile.is_open())
{
cout << "无法打开文件，可能文件不存在或者路径不对";
exit(EXIT_FAILURE);
}
cout << "请输入捐献者数目: ";
inFile >> n;
inFile.get();
cout << n << endl;
struct data *pf = new struct data[n];
for (int i = 0; i < n; ++i)
{
cout << "输入第" << i + 1 << "个捐献者的姓名: ";
inFile.getline(pf[i].name, SIZE);
cout << pf[i].name << endl;
cout << "输入第" << i + 1 << "个捐献者捐献的金额: ";
inFile >> pf[i].amount;
inFile.get();
cout << pf[i].amount << endl;
}
cout << "重要捐款人:\n";
int temp = 0;
for (int i = 0; i < n; ++i)
if (pf[i].amount > 10000)
{
cout << pf[i].name << endl;
++temp;
}
if (temp == 0)
cout << "none" << endl;
temp = 0;
cout << "其他捐献人:\n";
for (int i = 0; i < n; ++i)
if (pf[i].amount <= 10000)
{
cout << pf[i].name << endl;
++temp;
}
if (temp == 0)
cout << "none" << endl;
delete []pf;
return 0;
}
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