C++ Primer 第五版第三章习题答案
书籍版本：2019年9月第一版；王刚 杨巨峰译；电子工业出版社
编译器 ： win10 && VS2015
3.1
对之前的练习用using来声明，其余与之前一致。
3.2
#include "stdafx.h"
#include
#include
using namespace std;
int main()
{
//string line;
// 按行读入
//while(getline(cin,line))
//{
// cout << line << endl;
//}
// 按词读入
string word;
while(cin>>word)
{
cout << word << endl;
}
system("pause");
return 0;
}
3.3
string类忽略遇到第一个有效字符前的所有空格，遇到第一个有效字符之后所有空格都开始有效
getline跳过空格继续向下读取
3.4
#include "stdafx.h"
#include
#include
using namespace std;
int main()
{
string line1,line2;
cout << "请输入字符串1：";
cin >> line1;
cout << "请输入字符串2：";
cin >> line2;
if (line1 == line2)
{
cout << "两个字符串相等" << endl;
}
else
{
cout << "两个字符串不相等" << endl;
}
if (line1.size() == line2.size())
{
cout << "两个字符串长度相等" << endl;
}
else
{
cout << "两个字符串长度不相等" << endl;
}
system("pause");
return 0;
}
3.5
#include "stdafx.h"
#include
#include
using namespace std;
int main()
{
string line,strNoSpace,strSpace;
while (cin>>line)
{
if (line == "break;")
{
break;
}
strNoSpace = strNoSpace + line;
strSpace = strSpace + " ";
strSpace = strSpace + line;
}
cout << "不带空格：" << strNoSpace << endl;
cout << "带空格：" << strSpace << endl;
system("pause");
return 0;
}
3.6
#include "stdafx.h"
#include
#include
using namespace std;
int main()
{
string str("test");
for (auto &s : str)
{
s = 'x';
}
cout << str;
system("pause");
return 0;
}
3.7
可以将类型换位char，具体操作就是将上面的auto换成char；结果无变化；
3.8
#include "stdafx.h"
#include
#include
using namespace std;
int main()
{
string str("test");
int i = 0;
for (i = 0;i 3.9
不合法，s未赋初始值为空，没有s[0];
3.10
#include "stdafx.h"
#include
#include
using namespace std;
int main()
{
string str("test,test,test");
int i = 0;
for (i = 0;i 3.11
合法，类型为char
3.12
a 正确，创建了一个里面是整形向量的向量；
b 错误，类型不同无法拷贝
c 正确，创建了一个string向量，里面有10个值为null的string；
3.13
a 0个元素，空的
b 10个元素，都没有值
c 10个值为42的int元素
d 1个值为10的元素
e 两个元素，一个值为10，另一个为42
f 10个值为空的string元素，因为10不是string
g 10个值为hi的string元素；
3.14
#include "stdafx.h"
#include
#include
using namespace std;
int main()
{
int num;
vector vec;
while (cin>>num)
{
vec.push_back(num);
}
system("pause");
return 0;
}
3.15
#include "stdafx.h"
#include
#include
#include
using namespace std;
int main()
{
string str;
vector strVec;
while (cin>>str)
{
strVec.push_back(str);
}
system("pause");
return 0;
}
3.16
我之前的结果是对的，检验过了
3.17
#include "stdafx.h"
#include
#include
#include
using namespace std;
int main()
{
string str;
vector strVec;
while (cin>>str)
{
if (str == "break;")
{
break;
}
strVec.push_back(str);
}
for (int i = 0; i < strVec.size(); i++)
{
string strC = strVec.at(i);
for (int j = 0; j < strC.size(); j++)
{
toupper(strC[j]);
}
cout << strC << endl;
}
system("pause");
return 0;
}
3.18
不合法，改成
vector
int num = 42;
ivec.push_back(num);
3.19
vector
vector
vector
int num = 42;
for(int i = 0;i<10;i++)
{
ivec.push_back(num);
}
3.20
#include "stdafx.h"
#include
#include
#include
using namespace std;
int main()
{
string str;
vector strVec;
int num[10] = { 1,2,3,4,5,6,7,8,9 };
int m = 0;
while (m<10)
{
strVec.push_back(num[m]);
m++;
}
cout << "相连两个：";
for (int i = 0; i < strVec.size()-1; i++)
{
cout << strVec[i] + strVec[i + 1] << " ";
}
cout << endl;
cout << "头尾两个：";
for (int i = 0; i < strVec.size(); i++)
{
cout << strVec[i] + strVec[strVec.size()-1-i-1] << " ";
}
cout << endl;
system("pause");
return 0;
}
3.21
#include "stdafx.h"
#include
#include
#include
using namespace std;
int main()
{
string str;
vector strVec;
int num[10] = { 1,2,3,4,5,6,7,8,9,11 };
int m = 0;
while (m<10)
{
strVec.push_back(num[m]);
m++;
}
vector::iterator it;
for (it = strVec.begin(); it != strVec.end(); it++)
{
cout << *it << endl;
}
system("pause");
return 0;
}
3.22
#include "stdafx.h"
#include
#include
#include
using namespace std;
int main()
{
string str("test,test");
for (auto it = str.begin(); it != str.end(); it++)
{
*it = toupper(*it);
cout << *it ;
}
system("pause");
return 0;
}
3.23
=
#include "stdafx.h"
#include
#include
#include
using namespace std;
int main()
{
string str;
vector strVec = {1,2,3,4,5,6,7,8,9,10};
vector::iterator it;
for (it = strVec.begin(); it != strVec.end(); it++)
{
*it = *it * 2;
cout << *it << endl;
}
system("pause");
return 0;
}
3.24
#include "stdafx.h"
#include
#include
#include
using namespace std;
int main()
{
string str;
vector strVec = {1,2,3,4,5,6,7,8,9,10};
vector::iterator it;
int n = 1;
int sum;
// 连续两个相加
for (it = strVec.begin(); it != strVec.end()-1; it++)
{
sum = *it + *(it + 1);
cout << sum << endl;
}
system("pause");
return 0;
}
3.25
#include "stdafx.h"
#include
#include
#include
using namespace std;
int main()
{
string str;
vector strVec;
for (int i = 0; i < 10; i++)
{
int num;
cin >> num;
strVec.push_back(num);
}
vector core(11, 0);
vector::iterator it;
for (it = strVec.begin();it != strVec.end();it++)
{
int index = (*it) / 10;
core[index]++;
}
for (it = core.begin(); it != core.end(); it++)
{
cout << *it << " ";
}
system("pause");
return 0;
}
3.26
因为要求的mid是相对于从beg开始到end结束的中间值
3.27
a unsigned是非定长；
b 合法的
c 函数返回值是int型但是不是定值，所以是非定长的；
d fundamental有11个字符，字符串数组长度也设置为11缺少“\0”的位置
3.28
string sa[10] 与string sa2[10] 都为空，里面无值
int ia[10];里面值都为0；
int ia2[10];里面值都为随机值
#include "stdafx.h"
#include
#include
#include
using namespace std;
string sa[10];
int ia[10];
int main()
{
string sa2[10];
int ia2[10];
for (int i = 0; i < 10; i++)
{
cout << sa[i] << endl;
cout << ia[i] << endl;
cout << sa2[i] << endl;
cout << ia2[i] << endl;
cout << "分割线" << endl;
}
system("pause");
return 0;
}
3.29
数组只能定长，无法自动增长，缺少灵活性，在用之前不能确定需要的空间大小时很不方便；
3.30
ix 只能小与array_size，等于时越界，因为长度为array_size的数组下标范围为0到array_size-1；
3.31
#include "stdafx.h"
#include
using namespace std;
int main()
{
int a[10];
for (int i = 0; i < 10; i++)
{
a[i] = i;
}
for (int i = 0; i < 10; i++)
{
cout << a[i] << endl;
}
system("pause");
return 0;
}
3.32
#include "stdafx.h"
#include
using namespace std;
int main()
{
int a[10];
for (int i = 0; i < 10; i++)
{
a[i] = i;
}
for (int i = 0; i < 10; i++)
{
cout << a[i] << endl;
}
int a2[10];
for (int i = 0; i < 10; i++)
{
a2[i] = a[i];
}
vector vec;
for (int i = 0; i < 10; i++)
{
vec.push_back(i);
}
system("pause");
return 0;
}
3.33
不初始化里面的值都是随机值；
3.34
p1 += p2 - p1; 等价于 p1 = p2 - p1 + p1 = p2;
在p1p2不指向同一数组时非法；
3.35
#include "stdafx.h"
#include
using namespace std;
int main()
{
int a[10];
int* num = a;
for (int i = 0; i < 10; i++)
{
a[i] = 0;
cout << a[i] << endl;
}
system("pause");
return 0;
}
3.36
#include "stdafx.h"
#include
#include
#include
using namespace std;
int main()
{
int a[10],b[10];
int* numa = a;
int* numb = b;
for (int i = 0; i < 10; i++)
{
a[i] = i;
b[i] = 10 - i;
}
for (int i = 0; i < 10; i++)
{
if( *(numa+i) == *(numb+i) )
{
}
else
{
cout << "不相等" << endl;
break;
}
}
vector veca(10, 1);
vector vecb;
for (int i = 0; i < 10; i++)
{
vecb.push_back(i);
}
for (int i = 0; i < 10; i++)
{
if(!veca[i] == vecb[i])
{
cout << "不相等" << endl;
break;
}
}
system("pause");
return 0;
}
3.37
#include "stdafx.h"
#include
using namespace std;
int main()
{
const char ca[] = { 'h', 'e', 'l', 'l', 'o' };
const char* cp = ca;
while (*cp)
{
cout << *cp << endl;
++cp;
}
system("pause");
return 0;
}
结果如下：
3.38
指针就是地址，两个地址相加之后是未知的存在。
3.39
#include "stdafx.h"
#include
#include
using namespace std;
bool stringcomp(string str1, string str2)
{
if (str1 == str2)
{
return true;
}
else
{
return false;
}
}
bool cstringcomp(char s1[], char s2[])
{
if (strcmp(s1, s2) == 0)
{
return true;
}
else
{
return false;
}
}
int main()
{
string str1 = "hello";
string str2 = "hello!";
char ca1[] = { 'h', 'e', 'l', 'l', 'o' , '\0'};
char ca2[] = { 'h', 'e', 'l', 'l', 'o' , '!', '\0' };
cout << stringcomp(str1, str2) << endl;
cout << cstringcomp(ca1, ca2) << endl;
system("pause");
return 0;
}
3.40
#include "stdafx.h"
#include
#include
using namespace std;
int main()
{
char ca1[] = "hello";
char ca2[] = "world";
char str[11];
strcpy_s(str, ca1);
strcat_s(str, ca2);
cout < 因为我用的是VS2015，所以会自动提示strcmp与strcat是不安全的，原因是这些函数内部是不进行参数检测的（包括越界类的），微软担心使用这些会造成内存异常，所以就改写了同样功能的函数，改写了的函数进行了参数的检测，使用这些新的函数会更安全和便捷，而改写后安全的函数就是strcmp_s与strcat-s。
3.41
#include "stdafx.h"
#include
#include
using namespace std;
int main()
{
int a[6];
for (int i = 0; i < 6; i++)
{
a[i] = i;
}
vector intVec(begin(a), end(a));
for (int i = 0; i < intVec.size(); i++)
{
cout << intVec.at(i) << endl;
}
system("pause");
return 0;
}
3.42
#include "stdafx.h"
#include
#include
using namespace std;
int main()
{
int a[6];
for (int i = 0; i < 6; i++)
{
a[i] = i;
}
vector intVec(begin(a), end(a));
int a2[6];
for (int i = 0; i < intVec.size(); i++)
{
a2[i] = intVec.at(i);
cout << a2[i] << endl;
}
system("pause");
return 0;
}
3.43
#include "stdafx.h"
#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(&p)[4] : ia)
for (int q : p) cout << q << " ";
cout << endl;
for (size_t i = 0; i != 3; ++i)
for (size_t j = 0; j != 4; ++j) cout << ia[i][j] << " ";
cout << endl;
for (int(*p)[4] = ia; p != ia + 3; ++p)
for (int* q = *p; q != *p + 4; ++q) cout << *q << " ";
cout << endl;
system("pause");
return 0;
}
3.44
#include "stdafx.h"
#include
#include
using namespace std;
int main()
{
int ia[3][4] = { 0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11 };
using int_array = int[4];
for (int_array& p : ia)
for (int q : p) cout << q << " ";
cout << endl;
for (size_t i = 0; i != 3; ++i)
for (size_t j = 0; j != 4; ++j) cout << ia[i][j] << " ";
cout << endl;
for (int_array* p = ia; p != ia + 3; ++p)
for (int* q = *p; q != *p + 4; ++q) cout << *q << " ";
cout << endl;
system("pause");
return 0;
}
3.45
#include "stdafx.h"
#include
#include
using namespace std;
int main()
{
int ia[3][4] = { 0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11 };
// a range for to manage the iteration
for (auto& p : ia)
for (int q : p) cout << q << " ";
cout << endl;
// ordinary for loop using subscripts
for (size_t i = 0; i != 3; ++i)
for (size_t j = 0; j != 4; ++j) cout << ia[i][j] << " ";
cout << endl;
// using pointers.
for (auto p = ia; p != ia + 3; ++p)
for (int* q = *p; q != *p + 4; ++q) cout << *q << " ";
cout << endl;
system("pause");
return 0;
}