EOJ Monthly 2018.8
单点时限: 1.0 sec
内存限制: 256 MB
There is a $n \times m$ chessboard. Queen’s position right now is $(x,y)$.
Queen is the most powerful chess. It can be moved any number of unoccupied squares in a straight line vertically, horizontally, or diagonally (in all eight directions).
Bad Queen is a greedy queen. It wants to travel around all the blocks on the chessboard, but don’t want to take too many moves to make that happen. Please devise a route such that Bad Queen can visit all the blocks on the chessboard in exactly $nm-1$ moves. The current position is considered as visited.
输入格式
The input contains four space-separated integers $n,m,x,y$ ($1 \le x \le n \le 100$, $1 \le y \le m \le 100$, $nm > 1$).
输出格式
Output the move sequence in order. That is $nm-1$ lines. Each line contains a coordinate $(x,y)$, separated with space, which is the position after the move.
$x_1 \ y_1 \
x_2 \ y_2 \
\vdots \
x_{nm-1} \ y_{nm-1}$
$(x_i,y_i)$ must be a legal position on chessboard, which means $1 \le x_i \le n$, $1 \le y_i \le m$.
If there are multiple solutions available, you may output any of them.
样例
3 3 1 1
3 3 1 3 2 3 2 1 3 1 2 2 1 2 3 2
提示
Here is the route in the example. 0 is the starting position, and 1 to 8 are the visiting orders.
