#15947: DP想法
f(m,m)=1
f(n,m)=n/(n-m)*f(n-1, m)
n=10, m=5 ==>
F(0)=f(m,m)=1
F(1)=f(m+1,m)= (m+1)/1 * 1 = 6
F(2)=f(m+2,m)= (m+2)/2 * 6 = 21
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#23710: Re:DP想法
ZeroJudge Forum
f(m,m)=1
f(n,m)=n/(n-m)*f(n-1, m)
n=10, m=5 ==>
F(0)=f(m,m)=1
F(1)=f(m+1,m)= (m+1)/1 * 1 = 6
F(2)=f(m+2,m)= (m+2)/2 * 6 = 21
...