《C++ primer》第五版习题答案整理——第三章 字符串、向量组和数组
更新中
P75
练习3.1
3.1.1
#include
using std::cout;
using std::endl;
int main()
{
int sum = 0, val = 50;
while (val <= 100)
{
sum += val;
++val;
}
cout << "Sum of 50 to 100 inclusive is " << sum << endl;
return 0;
} 3.1.2
#include
using std::cout;
using std::endl;
int main()
{
int sum = 0;
for (int val = 10; val >= 0; --val)
{
sum += val;
}
cout << "Sum of 10 to 0 inclusive is " << sum << endl;
return 0;
} 3.1.3
#include
using std::cout;
using std::cin;
using std::endl;
int main()
{
cout << "请输入两个整数： " << endl;
int i = 0, j = 0;
cin >> i >> j;
if (i <= j)
{
for (i; i <= j; i++)
cout << i << endl;
}
else
{
for (i; i >= j; i--)
cout << i << stendl;
}
return 0;
} 3.1.4
#include
#include
#include "../ch02/ex2_42.h"
using std::cin;
using std::cout;
using std::endl;
using std::cerr;
int main()
{
Sales_data data1, data2;
// code to read into data1 and data2
double price = 0; // price per book, used to calculate total revenue
// read the first transactions: ISBN, number of books sold, price per book
cin >> data1.bookNo >> data1.units_sold >> price;
// calculate total revenue from price and units_sold
data1.revenue = data1.units_sold * price;
// read the second transaction
cin >> data2.bookNo >> data2.units_sold >> price;
data2.revenue = data2.units_sold * price;
// code to check whether data1 and data2 have the same ISBN
// and if so print the sum of data1 and data2
if (data1.bookNo == data2.bookNo)
{
unsigned totalCnt = data1.units_sold + data2.units_sold;
double totalRevenue = data1.revenue + data2.revenue;
// print: ISBN, total sold, total revenue, average price per book
cout << data1.bookNo << " " << totalCnt
<< " " << totalRevenue << " ";
if (totalCnt != 0)
cout << totalRevenue / totalCnt << endl;
else
cout << "(no sales)" << endl;
return 0; // indicate success
}
else
{ // transactions weren't for the same ISBN
cerr << "Data must refer to the same ISBN" << endl;
return -1; // indicate failure
}
} 不再一一列举；
知识点：using声明命名空间。注意的是头文件中不应该包含using声明，因为在引用头文件时，会将头文件中的内容拷贝到文件中来，如果头文件中包含了using声明，那么可能每一个头文件中都会包含using声明，可能会造成名字的冲突。
常加：using namespace std ;(将标准库声明)
P81
练习3.2
一整行
#include
#include
using namespace std;
int main()
{
string line;
while (getline(cin, line))
cout << line << endl;
return 0;
} 一个词
#include
#include
using namespace std;
int main()
{
string line;
while(cin>>line)
cout << line << endl;
return 0;
}
练习3.3
对于string类的输入函数，它会自动忽略开头的空白（空格、制表符、换行等等），从第一个真正的字符开始直到下一个空白。
对于getline()函数，它会保存字符串中的空白符，它读入数据，直到遇到换行符位置。
练习3.4
字符串比较
#include
#include
using namespace std;
int main()
{
string i,j;
cout << "请输入两个字符串" << endl;
cin >> i >> j;
if (i == j)
cout << "两字符串相等" << endl;
if (i != j)
{
if (i > j)
cout << "两字符串不相等，较大的是： " << i << endl;
else
cout << "两字符串不相等，较大的是： " << j << endl;
}
return 0;
} 字符串长度比较
#include
#include
using namespace std;
int main()
{
string i,j;
cout << "请输入两个字符串" << endl;
cin >> i >> j;
if (i.size() == j.size())
cout << "两字符串长度相等" << endl;
if (i.size()!= j.size())
{
if (i.size ()> j.size())
cout << "两字符串长度不相等，较大的是： " << i << endl;
else
cout << "两字符串长度不相等，较大的是： " << j << endl;
}
return 0;
}
练习3.5
连在一起
#include
#include
using namespace std;
int main()
{
string i,j;
cout<<"请输入多个字符串"<> j)
{
i += j;
}
cout << i << endl;
return 0;
} 空格分隔开
#include
#include
using namespace std;
int main()
{
string i,j;
cout<<"请输入多个字符串"<> j)
{
i += j+=" ";
}
cout << i << endl;
return 0;
}
P86
练习3.6
#include
#include
using namespace std;
int main()
{
string str;
cin >> str;
for (auto &c : str)//切记用引用
c='X';
cout << str << endl;
return 0;
}
练习3.7
不会发生变化，因为每一个元素都是char类型的。
#include
#include
using namespace std;
int main()
{
string str;
cin >> str;
for (char &c : str)//切记用引用
c='X';
cout << str << endl;
return 0;
}
练习3.8
个人感觉用哪个都差不多（所以到底哪个好？？？）。
传统for循环
#include
#include
using namespace std;
int main()
{
string str;
cin >> str;
int num = str.size();
for(int i=0;i while循环
#include
#include
using namespace std;
int main()
{
string str;
cin >> str;
int num = str.size();
int i=0;
while (i< num)
{
str[i] = 'X';
i++;
}
cout << str << endl;
return 0;
}
练习3.9
不合法，因为字符串S是一个空字符串，第一个元素是未知的，引用非法。
练习3.10
#include
#include
using namespace std;
int main()
{
string str,putout;
cout << "请输入一段带标点符号的字符串:" << endl;
cin >> str;
for (auto c : str)
if (!ispunct(c))
putout= putout + c;
cout << putout << endl;
return 0;
}
3.11
合法，c的类型为对const char的引用
P90
3.12
- 正确，包含0个元素；
- 错误，vector元素类型不一致；
- 正确，包含10个元素为“null”的vector对象。
3.13
- 空vector；
- 10个初始值为0的int对象；
- 10个初始值为42的int对象；
- 一个初始值为10的int对象；
- 2个int对象，初始值分别为10 42；
- 10个空字符串；
- 10个初始化为”hi”的字符串。
P91
3.14
#include
#include
#include
using namespace std;
int main()
{
int i;
vectorv{ 0 };
while (cin >> i)
v.push_back(i);
return 0;
}
3.15
#include
#include
#include
using namespace std;
int main()
{
string i;
vectorv;
while (cin >> i)
v.push_back(i);
return 0;
}
P94
练习3.16
#include
#include
#include
using namespace std;
int main()
{
vectorv1, v2(10), v3(10, 42), v4{ 10 }, v5{10,42};
vectorv6{ 10 }, v7{ 10,"hi" };
cout << v1.size()< 练习3.17
#include
#include
#include
using namespace std;
int main()
{
vector str;
string s;
cout << "请输入一组词：" << endl;
while (cin >> s)
{
str.push_back(s);
}
for (auto &c1 : str)
{
for(auto &c2:c1)
c2 = toupper(c2);
}
for (auto c : str)
{
cout << c << endl;
}
return 0;
}
练习3.18
不合法，空vector，给第一个元素赋值是错误的。
第二行改为：
int str = 42;
ivec.push_back(str);
练习3.19
vectorv1(10,42);//此法最好，简洁！
vectorv2{ 42,42,42,42,42,42,42,42,42,42 };
vectorv3 = { 42,42,42,42,42,42,42,42,42,42 };
vectorv4 = v1;
vectorv5(v1);
练习3.20
1.相邻整数相加
#include
#include
#include
using namespace std;
int main()
{
int in;
vectorin_v,sum1;
cout << "请输入一组整数" << endl;
while (cin >> in)
{
in_v.push_back(in);
}
for (int i = 0; i < in_v.size()-1; i++)
{
sum1.push_back(in_v[i] + in_v[i + 1]);
}
for (auto c : sum1)
{
cout << c << ' ';
}
cout << endl;
} 2.“头尾“整数相加
#include
#include
#include
using namespace std;
int main()
{
int in;
vectorin_v,sum2;
cout << "请输入一组整数" << endl;//分两种情况
while (cin >> in)
{
in_v.push_back(in);
}
if (in_v.size() % 2 == 0)//判断整数个数为双数
{
for (int i = 0; i < in_v.size() / 2 + 1; i++)
{
sum2.push_back(in_v[i] + in_v[in_v.size() - i - 1]);
}
for (auto c : sum2)
{
cout << c << ' ';
}
cout << endl;
}
else//整数个数为单数
{
for (int i = 0; i < in_v.size() / 2 + 1; i++)
{
sum2.push_back(in_v[i] + in_v[in_v.size() - i - 1]);
}
sum2.push_back(in_v[in_v.size() / 2]);
for (auto c : sum2)
{
cout << c << ' ';
}
cout << endl;
}
}
P99
练习3.21
#include
#include
#include
using namespace std;
int main()
{
vectorv1, v2(10), v3(10, 42), v4{ 10 }, v5{ 10,42 };
vectorv6{ 10 }, v7{ 10,"hi" };
cout << v1.size() << endl;
for (auto it=v1.begin();it!=v1.end();++it)
{
cout << *it<< ' ';
}
cout << endl;
cout << v2.size() << endl;
for (auto it = v2.begin(); it != v2.end(); ++it)
{
cout <<*it << ' ';
}
cout << endl;
cout << v3.size() << endl;
for (auto it = v3.begin(); it != v3.end(); ++it)
{
cout << *it << ' ';
}
cout << endl;
cout << v4.size() << endl;
for (auto it = v4.begin(); it != v4.end(); ++it)
{
cout << *it << ' ';
}
cout << endl;
cout << v5.size() << endl;
for (auto it = v5.begin(); it != v5.end(); ++it)
{
cout <<*it<< ' ';
}
cout << endl;
cout << v6.size() << endl;
for (auto it = v6.begin(); it != v6.end(); ++it)
{
cout <<*it << ' ';
}
cout << endl;
cout << v7.size() << endl;
for (auto it = v7.begin(); it != v7.end(); ++it)
{
cout <<*it<< ' ';
}
cout << endl;
return 0;
}
练习3.22
#include
#include
#include
using namespace std;
int main()
{
vector text{ "some string"," ","1asafd" };
for (auto it = text.begin(); it != text.end() && !it->empty(); ++it)
{
for (auto& c : *it)
c = toupper(c);
cout << *it << endl;
}
return 0;
}
练习3.23
#include
#include
#include
using namespace std;
int main()
{
vector num(10,6);
for (auto it = num.begin(); it != num.end(); ++it)
{
*it *= 2;
cout << *it << endl;
}
return 0;
}
P101
练习3.24
相邻相加
#include
#include
#include
using namespace std;
int main()
{
int in;
vectorin_v, sum;
cout << "请输入一组整数" << endl;
while (cin >> in)
{
in_v.push_back(in);
}
for (auto it = in_v.begin(); it + 1 != in_v.end(); ++it)
{
sum.push_back(*it + *(it + 1));
}
for (auto c : sum)
{
cout << c << " ";
}
cout << endl;
return 0;
} 头尾相加
#include
#include
#include
using namespace std;
int main()
{
int in;
vectorin_v, sum;
cout << "请输入一组整数" << endl;//分两种情况
while (cin >> in)
{
in_v.push_back(in);
}
if (in_v.size() % 2 == 0)//判断整数个数为双数
{
for (auto it_beg=in_v.begin(),it_end=in_v.end()-1;it_beg!=it_end;++it_beg,--it_end)
{
sum.push_back(*it_beg+*it_end);
}
for (auto c : sum)
{
cout << c << ' ';
}
cout << endl;
}
else//整数个数为单数
{
for (auto it_beg = in_v.begin(), it_end = in_v.end() - 1; it_beg != it_end; ++it_beg, --it_end)
{
sum.push_back(*it_beg + *it_end);
}
sum.push_back(in_v[in_v.size() / 2]);
for (auto c : sum)
{
cout << c << ' ';
}
cout << endl;
}
}
练习3.25
#include
#include
#include
using namespace std;
int main()
{
vectorscores(11, 0);
int grade;
while (cin >> grade)
{
auto it = scores.begin();
int n = grade / 10;
it = it + n;
++(*it);
}
for (auto c:scores)
{
cout < 练习3.26
因为两个迭代器之间没有相加的操作！
两迭代器相减的结果是他们之间的距离。
迭代器+n或-n分别为向前或向后移动若干元素。
P103
练习3.27
- 非法，维度必须为常量；
- 合法；
- 非法；
- 非法，没有空间存放空字符。
练习3.28
sa数组为空；ia数组含有10个整数，皆为0；sa2数组为空；ia2数组含有10个整数，在函数体内，值不确定
练习3.29
数组的缺点：数组的大小是确定不变的，不可以向数组中添加元素，丧失了vectoer的灵活性。
P104
练习3.30
数组大小为10，那么索引应该是0~9，数组越界ix < array_size
练习3.31
#include
using namespace std;
int main()
{
int ia[10];
for (int i = 0; i <= 9; i++)
ia[i] = i;
for (auto i : ia)
cout << i << " ";
cout << endl;
return 0;
}
练习3.32
数组
#include
using namespace std;
int main()
{
int ia[10];
int b[10];
for (int i = 0; i <= 9; i++)
{
ia[i] = i;
b[i] = ia[i];
}
for (auto i : ia)
cout << i << " " ;
cout << endl;
for (auto i : b)
cout << i << " ";
cout << endl;
return 0;
}
vector
#include
#include
using namespace std;
int main()
{
vectoriv1;
for (int j = 0; j < 10; j++)
iv1.push_back(j);
for (auto c : iv1)
cout << c << " ";
cout << endl;
vectoriv2(iv1);
for (auto c : iv2)
cout << c << " ";
cout << endl;
return 0;
}
练习3.33
数组的值为不确定的.
P108
练习3.34
将p1移动到p2位置，即将p1移动（p2-p1）个位置；p1或p2是非法的，该程序就是非法的。
练习3.35
#include
#include
using namespace std;
int main()
{
int ia[] = { 0,1,2,3,4,5 };
for (auto c : ia)
cout << c << ' ';
cout << endl;
int* p = ia;
for (int i = 0; i < 6; i++)
{
*p = 0;
++p;
}
for (auto c : ia)
{
cout << c << ' ';
}
cout << endl;
return 0;
}
练习3.36
数组比较
#include
#include
#include
using namespace std;
int main()
{
int a[10], b[10];
int* numa = a, * numb = b;
int temp=0;
for (int i = 0; i < 10; i++)
{
a[i] = i;
b[i] = 10-i;
}
if (sizeof(a) == sizeof(b))
{
for (int j = 0; j < 10; j++)
{
if (*(numa + j) == *(numb + j))
{
temp ++;
}
}
if (temp == 10)
{
cout << "相等" << endl;
}
else
cout << "不相等" << endl;
}
else
cout << "不相等" << endl;
return 0;
} vector比较
#include
#include
#include
using namespace std;
int main()
{
int a[10], b[10];
for (int i = 0; i < 10; i++)
{
a[i] = i;
b[i] = 10-i;
}
vector v1(a, a + 10);//一种新的用数组初始化vector的方法，
vector v2(b, b + 10);// 其元素与数组中元素相同。
if (v1 == v2)
cout << "相等" << endl;
else
cout << "不相等" << endl;
return 0;
}
P110
练习3.37
输出如下
练习3.38
指针指代的是对象的地址，相加是地址相加，难以区分到底什么意义。
练习3.39
#include
#include
#include
using namespace std;
int main()
{
string a = "abcd";
string b = "efgh";
if (a == b)
cout << "equal" << endl;
else
cout << "not equal" << endl;
char ca1[] = { 'a','b','c','\0' };
char ca2[] = "abc";
if (strcmp(ca1, ca2) == 0)
cout << "equal" << endl;
else
cout << "not equal";
return 0;
}
练习3.40
#include
#include
#include
#pragma warning(disable:4996)//VS2019编译错误，必须加上此行；
//原因是strcpy与strcat函数被新版本判定为不安全，准备弃用。
using namespace std;
int main()
{
char ca1[] = "abc";
char ca2[] = { 'd','e','f' ,'\0'};
char ca3[100];
strcpy(ca3, ca1);
strcat(ca3, ca2);
cout << ca3 << endl;
return 0;
}
P112
练习3.41
#include
#include
#include
using namespace std;
int main()
{
int a[] = { 1,2,3 };
vector b(begin(a), end(a));
for (auto c : b)
cout << c << ' ';
cout << endl;
return 0;
}
练习3.42
#include
#include
#include
using namespace std;
int main()
{
int a[10];
vector v(10,1);
for (int i=0;i<=9;i++)
{
a[i] = v[i];
cout << a[i] << ' ';
}
cout << endl;
return 0;
} P116
练习3.43
#include
#include
#include
using namespace std;
int main()
{
int ia[3][4] = {
{0,1,2,3},
{4,5,6,7},
{8,9,10,11}
};
for (const int(&i)[4] : ia)
{
for (int j : i)
cout << j << " ";
cout << endl;
}
cout << endl;
for (size_t i = 0; i < 3; i++)
{
for (size_t j = 0; j < 4; j++)
cout << ia[i][j] << " ";
cout << endl;
}
cout << endl;
for (int(*i)[4] = begin(ia); i != end(ia); i++)
{
for (int* j = begin(*i); j != end(*i); j++)
cout << *j << ' ';
cout << endl;
}
return 0;
}
练习3.44
#include
#include
#include
using namespace std;
int main()
{
using int_array=int[4];
int ia[3][4] = {
{0,1,2,3},
{4,5,6,7},
{8,9,10,11}
};
for (const int_array &i: ia)
{
for (int j : i)
cout << j << " ";
cout << endl;
}
cout << endl;
for (size_t i = 0; i < 3; i++)
{
for (size_t j = 0; j < 4; j++)
cout << ia[i][j] << " ";
cout << endl;
}
cout << endl;
for (int_array *i = begin(ia); i != end(ia); i++)
{
for (int* j = begin(*i); j != end(*i); j++)
cout << *j << ' ';
cout << endl;
}
return 0;
} 练习3.45
#include
#include
#include
using namespace std;
int main()
{
int ia[3][4] = {
{0,1,2,3},
{4,5,6,7},
{8,9,10,11}
};
for (auto &i: ia)
{
for (auto j : i)
cout << j << " ";
cout << endl;
}
cout << endl;
for (auto i = 0; i < 3; i++)
{
for (auto j = 0; j < 4; j++)
cout << ia[i][j] << " ";
cout << endl;
}
cout << endl;
for (auto *i = begin(ia); i != end(ia); i++)
{
for (auto * j = begin(*i); j != end(*i); j++)
cout << *j << ' ';
cout << endl;
}
return 0;
}