Input: 2
Ouput: 0 X X * * 1 X * 2 + +

Input: 3
Output: 0 X X X * * * 1 X X * * 2 X * 3 + + +

Input: 4
Output: 0 X X X X * * * * 1 X X X * * * 2 X X * * 3 X * 4 + + + +

In mathematics it's right, but here I'd got WA 2.

Why?

>>>>Output should contain a sequence of minimal length

your output could has not minimal length

OK, I'd got AC.
Here right examples:

Input: N = 2
Output: 0 X * 1 + X * 2 +

Input: N = 3
Output: 0 X * 1 + X * 2 + X * 3 +

And so on.

Edited by author 25.03.2009 20:20