C++Primer第五版习题答案（四）

4.21

#include <iostream>
#include <vector>

using namespace std;

int main()
{
	vector<int> ivec;
	for (int i = 0; i < 10; i++)
		ivec.push_back(i);

	for (auto& i : ivec)
	{
		i = (i & 0x1) ? (2 * i) : i;
	}
	
	for (auto& i : ivec)
		cout << i << " ";
	cout << endl;

	return 0;
}

4.22

#include <iostream>

using namespace std;

int main()
{
	int grade;
	cout << "请输入成绩：" << endl;
	cin >> grade;

	//a
	/*cout << ((grade > 90) ? "high pass" : ((grade > 75) ? "pass" : ((grade > 60) ? "low pass" : "fail")));*/

	//b
	if (grade > 90)
		cout << "high pass";
	else if (grade > 75)
		cout << "pass";
	else if (grade > 60)
		cout << "low pass";
	else
		cout << "fail";

	return 0;
}

4.28

#include <iostream>

using namespace std;

int main()
{
	
	cout << "sizeof(char) = " << sizeof(char) << endl;
	cout << "sizeof(wchar_t) = " << sizeof(wchar_t) << endl;
	cout << "sizeof(char16_t) = " << sizeof(char16_t) << endl;
	cout << "sizeof(char32_t) = " << sizeof(char32_t) << endl;
	cout << "====================" << endl;

	cout << "sizeof(short) = " << sizeof(short) << endl;
	cout << "sizeof(int) = " << sizeof(int) << endl;
	cout << "sizeof(long) = " << sizeof(long) << endl;
	cout << "sizeof(long long) = " << sizeof(long long) << endl;
	cout << "====================" << endl;

	cout << "sizeof(float) = " << sizeof(float) << endl;
	cout << "sizeof(double) = " << sizeof(double) << endl;
	cout << "sizeof(long double) = " << sizeof(long double) << endl;
	cout << "====================" << endl;

	cout << "sizeof(int8_t) = " << sizeof(int8_t) << endl;
	cout << "sizeof(uint8_t) = " << sizeof(uint8_t) << endl;
	cout << "sizeof(int16_t) = " << sizeof(int16_t) << endl;
	cout << "sizeof(uint16_t) = " << sizeof(uint16_t) << endl;
	cout << "sizeof(int32_t) = " << sizeof(int32_t) << endl;
	cout << "sizeof(uint32_t) = " << sizeof(uint32_t) << endl;
	cout << "sizeof(int64_t) = " << sizeof(int64_t) << endl;
	cout << "sizeof(uint64_t) = " << sizeof(uint64_t) << endl;

	return 0;
}