C++ primer5 4.21/4.22

使用条件运算符从vector中找到哪些元素的值是奇数，然后将这些奇数值翻倍。

//4.21
#include 
#include 
using namespace std;

int main()
{
    vector<int> vec = {0,1,2,3,4,5,6,7,8,9};
	for (auto i : vec)
	     cout << ((i%2) ? i*2 : i) << " "; //使用条件运算符找出原vector对象中的奇数值并翻倍
	cout << endl;
	system("pause");
    return 0;
}

将成绩划分成四种，分别使用条件运算符和if语句判断

//4.22
#include 
using namespace std;

int main()
{
	unsigned grade;
	while(cin >> grade)
    //for(unsigned grade; cin >> grade; ) //不断输入分数，遇到ctrl+Z为止
	{
		//条件运算符版本
		auto result = grade>90 ? "high pass" : grade<60 ? "fail" : grade<75? "low pass" : "pass";
		cout << result << endl;

		//if语句
		if (grade > 90)         
		    cout << "high pass"; //if成立
        else if (grade < 60)     //前面的if不成立，接着判断
		    cout << "fail";
        else if (grade < 75)    
		    cout << "low pass";
        else                
		    cout << "pass";
        cout << endl;
	}
	cout << endl;

	system("pause");
    return 0;
}