C++——枚举

枚举类型
1.enum 枚举关键字
类型定义，例如：
enmu weekday {Sun, Mon, Tue, Wed, Thu, Fri, Sat};
Sun = 0, Mon = 1, Tue = 2…Sat = 6;
或者
enum weekday {Sun=7, Mon=1, Tue, Wed, Thu, Fri, Sat};
Sun = 7, Mon = 1, Tue = 2, Wed = 3 …Sat = 6;

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2.变量定义，例如：
enum weekday day1, day2;
或者
enum weekday {Sun, Mon, Tue, Wed, Thu, Fri, Sat}day1,day2;

例如：
输入三个数，判断它是什么三角形。

#include <iostream>

using namespace std;
int main()
{
     int a , b, c;
     enum triangle {scalene,isosceles, equilateral, notriangle};
     enum triangle tri;

     cout << "请输入三个边长\n";
     cin >> a >> b >> c;
     if(a == b && b == c && b == c)
     {
         tri = equilateral;

     }
     else if(a + b <= c || a + c <= b || b + c <= a)
     {
         tri = notriangle;
     }
     else if(a == b || b == c || a == c)
     {
         tri = isosceles;
     }
     else
        tri = scalene;

    switch (tri)
    {
        case scalene:
             cout << "scalene triangle" << endl;
             break;
        case isosceles:
             cout << "isosceles triangle" << endl;
             break;
        case equilateral:
             cout << "equilateral triangle" << endl;
             break;
        case notriangle:
             cout << "notriangle triangle" << endl;
             break;

    }


    return 0;
}

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作用：
1.限制数据范围；
2.防止出现垃圾数据；
3.可以讲数值与指定的名称相匹配。