C++primer 习题第三章

//3.2.1
#include<iostream>
#include<string>

using namespace std;
int main()
{
	string line;
	cout << "请输入你要输入的字符串，一行：" << endl;
	while (getline(cin, line))
	{
		cout << line << endl;
	}
	return 0;
}
//3.2.2
#include<iostream>
#include<string>

using namespace std;
int main()
{
	string word;
	cout << "请输入你要输入的字符串，一个词：" << endl;
	while (cin>>word)
	{
		cout << word << endl;
	}
	return 0;
}

3.3 标准库string的输入运算符自动忽略开头的空格、换行、制表符等，从第一个真正的字符开始读起，知道遇见下一个空白。

getline从任意字符开始，知道遇见换行符。

//3.4.1
#include<iostream>
#include<string>

using namespace std;
int main()
{
	string str1,str2;
	cout << "请输入两个字符串：" << endl;
	cin >> str1 >> str2;
	if(str1==str2)
	{
		cout <<"epual"<< endl;
	}
	else if (str1 > str2)
	{
		cout << str1 << ">" << str2 << endl;
	}
	else if (str1 <str2)
	{
		cout << str1 << "<" << str2 << endl;
	}
	return 0;
}
//3.4.2
using namespace std;
int main()
{
	string str1,str2;
	cout << "请输入两个字符串：" << endl;
	cin >> str1 >> str2;
	auto len1 = str1.size();
	auto len2 = str2.size();
	if(len1==len2)
	{
		cout <<"epual"<< endl;
	}
	else if (len1 > len2)
	{
		cout << str1 << ">" << str2 << endl;
	}
	else if (len1 <len2)
	{
		cout << str1 << "<" << str2 << endl;
	}
	return 0;
}

//3.5.1
#include<iostream>
#include<string>

using namespace std;
int main()
{
	string s,ss;
	char ch = 'y';
	cout << "请输入第一个字符串：" << endl;
	while (cin >> s)
	{
		ss += s;
		cout << "是否继续输入字符串y or n：" << endl;
		cin >> ch;
		if (ch == 'y' || ch == 'Y')//用单引号。双引号错误，双引号是字符串指针
			cout << "请输入下一个字符串："<<endl;
		else
			break;
	}
	cout << ss << endl;
	return 0;
}
//3.5.2

#include<iostream>
#include<string>

using namespace std;
int main()
{
	string s,ss;
	char ch = 'y';
	cout << "请输入第一个字符串：" << endl;
	while (cin >> s)
	{
		if (!ss.size())
			ss += s;
		else
			ss = ss + " " + s;
		cout << "是否继续输入字符串y or n：" << endl;
		cin >> ch;
		if (ch == 'y' || ch == 'Y')
			cout << "请输入下一个字符串："<<endl;
		else
			break;
	}
	cout << ss << endl;
	return 0;
}

//3.6
#include<iostream>
#include<string>

using namespace std;
int main()
{
	string s;
	cout << "请输入一个字符串,可以包含空白：" << endl;
	getline(cin, s);
	for(auto &c : s)
	{
		c = 'X';
	}
	cout << s << endl;
	return 0;
}

//3.8.1
#include<iostream>
#include<string>

using namespace std;
int main()
{
	string s;
	cout << "请输入一个字符串可以包含空格：" << endl;
	getline(cin, s);
	int i = 0;
	while (s[i] != '\0')
	{
		s[i] = 'X';
		i++;
	}
	cout << s << endl;
	return 0;
}
//3.8.2
#include<iostream>
#include<string>

using namespace std;
int main()
{
	string s;
	cout << "请输入一个字符串可以包含空格：" << endl;
	getline(cin, s);
	unsigned int i = 0;
	for (i = 0;i<s.size();i++)
	{
		s[i] = 'X';
	}
	cout << s << endl;
	return 0;
}

//3.10.1
#include<iostream>
#include<string>
#include<cctype>

using namespace std;
int main()
{
	string s;
	cout << "请输入一个字符串可以包含空格：" << endl;
	getline(cin, s);

	for (auto c : s)
	{
		if(!ispunct(c))
			cout << c;
	}
	return 0;
}
//3.10.2
#include<iostream>
#include<string>
#include<cctype>

using namespace std;
int main()
{
	string s;
	cout << "请输入一个字符串可以包含空格：" << endl;
	getline(cin, s);

	for (decltype(s.size()) i = 0;i<s.size();i++)
	{
		if(!ispunct(s[i]))
			cout << s[i];
	}
	return 0;
}

//3.14
#include<iostream>
#include<vector>

using namespace std;
int main()
{
	int i;
	char cont = 'y';
	vector<int> ii;
	cout << "请输入一组整数：" << endl;
	while (cin >> i)
	{
		ii.push_back(i);
		cout << "continue? y or n?" << endl;
		cin >> cont;
		if (cont != 'y' && cont != 'Y')
			break;
	}
	for (auto elem : ii)
	{
		cout << elem << " ";
	}
	return 0;
}

//3.15
#include<iostream>
#include<string>
#include<vector>

using namespace std;
int main()
{
	string s;
	char cont = 'y';
	vector<string> ss;
	cout << "请输入一组字符串：" << endl;
	while (cin >> s)
	{
		ss.push_back(s);
		cout << "continue? y or n?" << endl;
		cin >> cont;
		if (cont != 'y' && cont != 'Y')
			break;
	}
	for (auto elem : ss)
	{
		cout << elem << " ";
	}
	return 0;
}

//3.16
#include<iostream>
#include<string>
#include<vector>

using namespace std;
int main()
{
	vector<int> v1;
	vector<int> v2(10);
	vector<int> v3(10,42);
	vector<int> v4{10};
	vector<int> v5{10,42};
	vector<string> v6{10};
	vector<string> v7{10,"hi"};
	cout << "v1元素的个数是：" << v1.size() << endl;
	if (v1.size() > 0)
	{
		cout << "v1的元素分别是：" << endl;
		for (auto elem : v1)
		{
			cout << elem << " ";
		}
		cout << endl;
	}
	cout << "v2元素的个数是：" << v2.size() << endl;
	if (v2.size() > 0)
	{
		cout << "v2的元素分别是：" << endl;
		for (auto elem : v2)
		{
			cout << elem << " ";
		}
		cout << endl;
	}
	cout << "v3元素的个数是：" << v3.size() << endl;
	if (v3.size() > 0)
	{
		cout << "v3的元素分别是：" << endl;
		for (auto elem : v3)
		{
			cout << elem << " ";
		}
		cout << endl;
	}
	cout << "v4元素的个数是：" << v4.size() << endl;
	if (v4.size() > 0)
	{
		cout << "v4的元素分别是：" << endl;
		for (auto elem : v4)
		{
			cout << elem << " ";
		}
		cout << endl;
	}
	cout << "v5元素的个数是：" << v5.size() << endl;
	if (v5.size() > 0)
	{
		cout << "v5的元素分别是：" << endl;
		for (auto elem : v5)
		{
			cout << elem << " ";
		}
		cout << endl;
	}
	cout << "v6元素的个数是：" << v6.size() << endl;
	if (v6.size() > 0)
	{
		cout << "v6的元素分别是：" << endl;
		for (auto elem : v6)
		{
			cout << elem << " ";
		}
		cout << endl;
	}
	cout << "v7元素的个数是：" << v7.size() << endl;
	if (v7.size() > 0)
	{
		cout << "v1的元素分别是：" << endl;
		for (auto elem : v7)
		{
			cout << elem << " ";
		}
		cout << endl;
	}
	return 0;
}

//3.17
#include<iostream>
#include<string>
#include<vector>
#include<cctype>

using namespace std;
int main()
{
	char cont = 'y';
	string word;
	vector<string> ss;
	cout << "请输入一组词：" << endl;
	while (cin >> word)
	{
		ss.push_back(word);
		cout << "continue? y or n" << endl;
		cin >> cont;
		if (cont != 'y'&&cont != 'Y')
			break;
	}
	for (auto &r : ss)
	{
		for (auto &c : r)
		{
			c = toupper(c);
		}
		cout << r << endl;
	}
	return 0;
}

//3.20.1
#include<iostream>
#include<vector>

using namespace std;
int main()
{
	char cont = 'y';
	unsigned int num = 0;
	int i;
	vector<int> vi;
	cout << "请输入一组整数：" << endl;
	while (cin >> i)
	{
		vi.push_back(i);
		cout << "continue? y or n" << endl;
		cin >> cont;
		if (cont != 'y'&&cont != 'Y')
			break;
	}
	for (decltype(vi.size()) j = 0;j<vi.size()-1;j += 2)
	{
		cout << vi[j] + vi[j + 1] << " ";
		if ((j + 2) % 10 == 0)
			cout << endl;
	}
	if (vi.size() % 2 != 0)
		cout << vi[vi.size() - 1];
	return 0;
}
//3.20.2
#include<iostream>
#include<vector>

using namespace std;
int main()
{
	char cont = 'y';
	unsigned int num = 0;
	int i;
	vector<int> vi;
	cout << "请输入一组整数：" << endl;
	while (cin >> i)
	{
		vi.push_back(i);
		cout << "continue? y or n" << endl;
		cin >> cont;
		if (cont != 'y'&&cont != 'Y')
			break;
	}
	if (vi.size() == 0)
	{
		cout << "无元素"<<endl;
		return -1;

	}
	for (decltype(vi.size()) j = 0;j<vi.size()/2;j++)
	{
		cout << vi[j] + vi[vi.size()-j-1] << " ";
		if ((j + 1) % 5 == 0)
			cout << endl;
	}
	if (vi.size() % 2 != 0)
		cout << vi[vi.size()/2];
	return 0;
}

//3.21
#include<iostream>
#include<string>
#include<vector>

using namespace std;
int main()
{
	vector<int> v1;
	vector<int> v2(10);
	vector<int> v3(10, 42);
	vector<int> v4{ 10 };
	vector<int> v5{ 10,42 };
	vector<string> v6{ 10 };
	vector<string> v7{ 10,"hi" };
	cout << "v1元素的个数是：" << v1.size() << endl;
	if (v1.cbegin()!=v1.cend())
	{
		cout << "v1的元素分别是：" << endl;
		for (auto it = v1.cbegin();it != v1.cend();++it)
		{
			cout << *it << " ";
		}
		cout << endl;
	}
	cout << "v2元素的个数是：" << v2.size() << endl;
	if (v2.cbegin() != v2.cend())
	{
		cout << "v2的元素分别是：" << endl;
		for (auto it = v2.cbegin();it != v2.cend();++it)
		{
			cout << *it << " ";
		}
		cout << endl;
	}
	cout << "v3元素的个数是：" << v3.size() << endl;
	if (v3.cbegin() != v3.cend())
	{
		cout << "v3的元素分别是：" << endl;
		for (auto it = v3.cbegin();it != v3.cend();++it)
		{
			cout << *it << " ";
		}
		cout << endl;
	}
	cout << "v4元素的个数是：" << v4.size() << endl;
	if (v4.cbegin() != v4.cend())
	{
		cout << "v4的元素分别是：" << endl;
		for (auto it = v4.cbegin();it != v4.cend();++it)
		{
			cout << *it << " ";
		}
		cout << endl;
	}
	cout << "v5元素的个数是：" << v5.size() << endl;
	if (v5.cbegin() != v5.cend())
	{
		cout << "v5的元素分别是：" << endl;
		for (auto it = v5.cbegin();it != v5.cend();++it)
		{
			cout << *it << " ";
		}
		cout << endl;
	}
	cout << "v6元素的个数是：" << v6.size() << endl;
	if (v6.cbegin() != v6.cend())
	{
		cout << "v6的元素分别是：" << endl;
		for (auto it = v6.cbegin();it != v6.cend();++it)
		{
			cout << *it << " ";
		}
		cout << endl;
	}
	cout << "v7元素的个数是：" << v7.size() << endl;
	if (v7.cbegin() != v7.cend())
	{
		cout << "v7的元素分别是：" << endl;
		for (auto it = v7.cbegin();it != v7.cend();++it)
		{
			cout << *it << " ";
		}
		cout << endl;
	}
	return 0;
}

//3.22
#include<iostream>
#include<string>
#include<vector>

using namespace std;
int main()
{
	vector<string> text;
	string s;
	cout << "input a sentence:" << endl;
	while (getline(cin,s))
	{
		text.push_back(s);
		break;
	}
	for (auto it = text.begin();it != text.end() && !it->empty();it++)
	{
		for (auto it1 = it->begin();it1 != it->end() ;it1++)
		{
			*it1 = toupper(*it1);
		}
		cout << *it << endl;
	}
	return 0;
}

//3.23
#include<iostream>
#include<ctime>
#include<vector>
#include<cstdlib>

using namespace std;
int main()
{
	vector<int> vi;
	srand((unsigned)time(NULL));
	for (int i = 0;i < 10;i++)
	{
		vi.push_back(rand() % 1000);
	}
	cout << "10个随机数:" <<endl;
	for (auto it = vi.cbegin();it != vi.cend();it++)
	{
		cout << *it << " ";
	}
	cout << endl;
	for (auto it = vi.begin();it != vi.end();it++)
	{
		*it *= 2;
		cout << *it << " ";
	}
	cout << endl;
	return 0;
}

//3.24.1
#include<iostream>
#include<vector>

using namespace std;
int main()
{
	char cont = 'y';
	unsigned int num = 0;
	int i;
	vector<int> vi;
	cout << "请输入一组整数：" << endl;
	while (cin >> i)
	{
		vi.push_back(i);
		cout << "continue? y or n" << endl;
		cin >> cont;
		if (cont != 'y'&&cont != 'Y')
			break;
	}
	if (vi.cbegin() == vi.cend())
	{
		cout << "no elem" << endl;
		return -1;
	}
	cout << "相邻两相和依次是：" << endl;
	for (auto it = vi.cbegin();it!=vi.cend()-1;it++)
	{
		cout << (*it+*(++it)) << " ";
		if ((it-vi.cbegin ()+1)%10 == 0)
			cout << endl;
	}
	if (vi.size() % 2 != 0)
		cout << *(vi.cend ()-1);
	return 0;
}
//3.24.2
#include<iostream>
#include<vector>

using namespace std;
int main()
{
	char cont = 'y';
	unsigned int num = 0;
	int i;
	vector<int> vi;
	cout << "请输入一组整数：" << endl;
	while (cin >> i)
	{
		vi.push_back(i);
		cout << "continue? y or n" << endl;
		cin >> cont;
		if (cont != 'y'&&cont != 'Y')
			break;
	}
	if (vi.cbegin() == vi.cend())
	{
		cout << "no elem" << endl;
		return -1;
	}
	cout << "相邻两相和依次是：" << endl;
	auto beg = vi.begin();
	auto end = vi.end();
	for (auto it = beg;it!=(end-beg)/2 + beg;it++)
	{
		cout << (*it + *(beg + (end - it)-1)) << " ";
		if ((it-beg+1)%5 == 0)
			cout << endl;
	}
	if (vi.size() % 2 != 0)
		cout << *((end - beg) / 2 + beg);
	return 0;
}

//3.2.25
#include<iostream>
#include<vector>

using namespace std;
int main()
{
	char cont = 'y';
	unsigned int num = 0;
	int i;
	vector<unsigned> vi(11);
	auto it = vi.begin();
	cout << "请输入0~100的数：" << endl;
	while (cin >> i)
	{
		if (i <= 100)
		{
			++*(it + i / 10);
		}
		cout << "continue?y or n?" << endl;
		cin >> cont;
		if (cont != 'y'&&cont != 'Y')
			break;
	}
	for (it = vi.begin();it != vi.end();it++)
	{
		cout << *it << " ";
	}
	return 0;
}

//3.31
#include<iostream>
#include<cstddef>

using namespace std;
int main()
{
	constexpr size_t num = 10;
	int arr[num];
	for (int i = 0;i < num;i++)
	{
		arr[i] = i;
	}
	for (auto j : arr)
	{
		cout << j << " ";
	}
	return 0;
}

//3.32.1
#include<iostream>
#include<cstddef>

using namespace std;
int main()
{
	constexpr size_t num = 10;
	int arr[num];
	int arr1[num];
	for (int i = 0;i < num;i++)
	{
		arr[i] = i;
		arr1[i] = arr[i];
	}
	for (auto j : arr1)
	{
		cout << j << " ";
	}
	return 0;
}
//3.32.2
#include<iostream>
#include<vector>

using namespace std;
int main()
{
	const int num = 10;
	vector<int> arr;
	vector<int> arr1;
	for (int i = 0;i < num;i++)
	{
		arr.push_back(i);
	}
	for (int j = 0;j < num;j++)
	{
		arr1.push_back(arr[j]);
	}
	for (auto j : arr1)
	{
		cout << j << " ";
	}
	return 0;
}

//3.35
#include<iostream>

using namespace std;
int main()
{
	int arr[10] = { 1,2,3,4,5,6,7,8,9,10 };
	int *p = arr;
	for (int i = 0;i < 10;i++)
	{
		*p = 0;
		++p;
	}
	for (auto e : arr)
	{
		cout << e << " ";
	}
	return 0;
}

//3.36
#include<iostream>
#include<cstddef>

using namespace std;
int main()
{
	const int size = 5;
	int arr[size], arr1[size];
	int i,j;
	int *beg = begin(arr);
	int *ed = end(arr);
	int *beg1 = begin(arr1);
	int *ed1 = end(arr1);
	cout << "input arr:" << endl;
	//输入数组1
	while (cin >> i)
	{
		if (beg != ed)
		{
			*beg = i;
			beg++;
		}
		if(beg == ed)
		{
			beg = begin(arr);
			break;
		}
	}
	cout << "input arr1" << endl;
	//输入数组2
	while (cin >> j)
	{
		if (beg1 != ed1)
		{
			*beg1 = j;
			beg1++;
		}
		if(beg1 == ed1)
		{
			beg1 = begin(arr1);//输入完
			break;
		}
	}
	while (beg != ed)
	{
		if (*beg == *beg1)
		{
			beg++;
			beg1++;
		}
		else
		{
			cout << "不相等" << endl;
			break;
		}
		if (beg == ed)
		{
			cout << "arr==arr1" << endl;
		}
	}
	return 0;
}
//3.36.2
#include<iostream>
#include<vector>

using namespace std;
int main()
{
	vector<int> v1, v2;
	int i;
	size_t num = 0;
	cout << "input v1" << endl;
	//输入vector1
	while (cin >> i)
	{
		v1.push_back(i);
		num++;
		if (num == 5)
		{
			num = 0;
			break;
		}
	}
	for (auto e : v1)
	{
		cout << e << " ";
	}
	cout << endl;
	cout << "input v2" << endl;
	//输入vector2
	while (cin >> i)
	{
		v2.push_back(i);
		num++;
		if (num == 5)
		{
			num = 0;
			break;
		}
	}
	for (auto e : v2)
	{
		cout << e << " ";
	}
	cout << endl;
	auto beg1 = v1.cbegin(), ed1 = v1.cend();
	auto beg2 = v2.cbegin(), ed2 = v2.cend();
	while (beg1 != ed1)
	{
		if (*beg1 != *beg2)
		{
			cout << "不相等" << endl;
		}
		beg1++;
		beg2++;	
	}
	cout << "arr==arr1" << endl;
	return 0;
}

//3.39.1
#include<iostream>
#include<string>

using namespace std;
int main()
{
	string s1, s2;
	cout << "input s1:" << endl;
	cin >> s1;
	cout << "input s2:" << endl;
	cin >> s2;
	if (s1 == s2)
	{
		cout << "s1=s2" << endl;
	}
	else
		cout << "s1!=s2" << endl;
}
//3.39.2
#include<iostream>
#include<cstring>

using namespace std;
int main()
{
	char s1[20], s2[20];
	cout << "input s1:" << endl;
	cin >> s1;
	cout << "input s2:" << endl;
	cin >> s2;
	if(strcmp(s1,s2))
	{
		cout << "s1!=s2" << endl;
	}
	else
		cout << "s1=s2" << endl;
}

//3.40
#include<iostream>
#include<cstring>

using namespace std;
int main()
{
	char s1[] = "hello", s2[] = " world!",s3[50];
	strcpy(s3, strcat(s1, s2));
	cout << s3 << endl;
	return 0;
}

//3.41
#include<iostream>
#include<vector>

using namespace std;
int main()
{
	char s1[] = { 0,1,2,3,4 };
	vector<int> vi(begin(s1),end(s1));
	for (auto e : vi)
	{
		cout << e << " ";
	}
	return 0;
}

//3.42
#include<iostream>
#include<vector>
#include<ctime>
#include<cstdlib>

using namespace std;
int main()
{
	vector<int> vi;
	const int siz = 10;
	srand((unsigned)time(NULL));
	for (int i = 0;i != siz;i++)
	{
		vi.push_back(rand() % 100);
		cout << vi[i] << " ";
	}
	cout << endl;
	auto it = vi.begin();
	int arr[siz];
	for (auto &e : arr)
	{
		e = *it;
		it++;
		cout << e << " ";
	}
	return 0;
}

//3.43
#include<iostream>

using namespace std;
int main()
{
	int ia[3][4] = { 1,2,3,4,1,2,3,4,1,2,3,4 };
	cout << "使用范围for管理循环"<<endl;
	for (int(&row)[4] : ia)
	{
		for (int col : row)
		{
			cout << col << " ";
		}
		cout << endl;
	}
	cout << "使用下表运算符" << endl;
	for (int i = 0;i != 3;i++)
	{
		for (int j = 0;j != 4;j++)
		{
			cout << ia[i][j] << " ";
		}
		cout << endl;
	}
	cout << "使用指针" << endl;
	for (int (*p)[4] = ia;p != ia + 3;p++)
	{
		for (int *q  = *p;q!= *p+4;q++)
		{
			cout << *q << " ";
		}
		cout << endl;
	}
	return 0;
}

//3.44
#include<iostream>

using namespace std;
using int_array = int[4];
int main()
{
	int ia[3][4] = { 1,2,3,4,1,2,3,4,1,2,3,4 };
	cout << "使用范围for管理循环"<<endl;
	for (int_array &row : ia)
	{
		for (int col : row)
		{
			cout << col << " ";
		}
		cout << endl;
	}
	cout << "使用下表运算符" << endl;
	for (int i = 0;i != 3;i++)
	{
		for (int j = 0;j != 4;j++)
		{
			cout << ia[i][j] << " ";
		}
		cout << endl;
	}
	cout << "使用指针" << endl;
	for (int_array *p = ia;p != ia + 3;p++)
	{
		for (int *q  = *p;q!= *p+4;q++)
		{
			cout << *q << " ";
		}
		cout << endl;
	}
	return 0;
}

//3.45
#include<iostream>

using namespace std;
int main()
{
	int ia[3][4] = { 1,2,3,4,1,2,3,4,1,2,3,4 };
	cout << "使用范围for管理循环"<<endl;
	for (auto &row : ia)
	{
		for (auto col : row)
		{
			cout << col << " ";
		}
		cout << endl;
	}
	cout << "使用下表运算符" << endl;
	for (auto i = 0;i != 3;i++)
	{
		for (auto j = 0;j != 4;j++)
		{
			cout << ia[i][j] << " ";
		}
		cout << endl;
	}
	cout << "使用指针" << endl;
	for (auto *p = ia;p != ia + 3;p++)
	{
		for (auto *q  = *p;q!= *p+4;q++)
		{
			cout << *q << " ";
		}
		cout << endl;
	}
	return 0;
}