作者KFS (oh)
看板Grad-ProbAsk
标题Re: [理工] [离散]-排列组合
时间Thu Aug 6 03:08:54 2009
※ 引述《IDontBite (大便兔子)》之铭言：
: 从坐标原点(0,0)走到(n,n),
: 走法只能往上或往右(每步1单位),
: 自己的 y 座标必须恒小於等於 x 座标,
: (也就是必须在 x = y 这条线下方)
: 问走法有几种?
: 答案是
: 2n
: C
: n
: _________
: (n+1)
: 想了好久都不懂为什麽, 有请高手0.0
Catalan numbers
the Catalan numbers form a sequence of natural numbers that occur in various counting problems, often involving recursively defined objects.
They are named for the Belgian mathematician Eugene Charles Catalan
The nth Catalan number is given directly in terms of binomial coefficients by
2n
: C
: n
: _________
: (n+1)
--
※ 发信站: 批踢踢实业坊(ptt.cc)
◆ From: 118.171.124.225