ri=28+(ri%4==0&&ri%100!=0 || ri%400==0);这句括号里的是什么意思啊？？？个人理解的很模糊！！！请大哥帮帮忙解释下


#include <iostream.h>
int main()
{
    int nian,yue,ri;
    cout<<"nian="<<endl<<"yue"<<endl;
    cin>>nian>>yue;
    switch(yue)
    {
        case 1:
        case 3:
        case 5:
        case 7:
        case 8:
        case 10:
        case 12:ri=31;
            break;
        case 4:
        case 6:   
        case 9:
        case 11:ri=30;
            break;
        case 2: ri=28+(ri%4==0&&ri%100!=0 || ri%400==0);
            break;
    }
    cout<<"ri="<<ri<<endl;
    cin.get();
    return 0;
}

没人在吗

这个我知道，能否详细点，如nian%4==0&&nian%100!=0,怎么解释这句话？？？

谢谢啊！很详细