Iscream12138的博客

POJ1276 之前看过一遍背包九讲，没有深刻体会，今天碰到了多重背包的模板题=。= Problem:Cash Machine Description A Bank plans to install a machine for cash withdrawal. The machine is able to deliver appropriate @ bills for a reques...

我们印象中计算组合数的公式 C(kn)=A(kn)A(kk)C\binom{k}{n}=\frac{A{k \choose n}}{A{k \choose k}}但其实，还有另外一个，常见于编程使用 C(kn)=C(k−1n−1)+C(kn−1)C{k \choose n}=C{k-1 \choose n-1}+C{k \choose n-1}Problem：挑选子集Description 给