F. Finding the Order (图形判断 / 判平行边) 2020牛客暑期多校训练营（第四场）

传送门

思路： AB//CD总共就三种情况分类讨论即可.

代码实现：

#include
#define endl '\n'
#define null NULL
#define ll long long
#define int long long
#define pii pair
#define lowbit(x) (x &(-x))
#define ls(x) x<<1
#define rs(x) (x<<1+1)
#define me(ar) memset(ar, 0, sizeof ar)
#define mem(ar,num) memset(ar, num, sizeof ar)
#define rp(i, n) for(int i = 0, i < n; i ++)
#define rep(i, a, n) for(int i = a; i <= n; i ++)
#define pre(i, n, a) for(int i = n; i >= a; i --)
#define IOS ios::sync_with_stdio(0); cin.tie(0);cout.tie(0);
const int way[4][2] = {{1, 0}, {-1, 0}, {0, 1}, {0, -1}};
using namespace std;
const int  inf = 0x7fffffff;
const double PI = acos(-1.0);
const double eps = 1e-6;
const ll   mod = 1e9 + 7;
const int  N = 2e5 + 5;

int t, a, b, c, d;

signed main()
{
    IOS;

    cin >> t;
    while(t --){
        cin >> a >> b >> c >> d;
        if((a < b && (d - c < b - a)) || (a > b && c > d &&(a - b < c - d)) || (a == b && c > d))
            cout << "AB//CD" << endl;
        else cout << "AB//DC" << endl;
    }

    return 0;
}