[理工] 鴿籠原理
5.修改pigeonhole principle 打網球例子:在三星期
之假期中，Herbert 每天至少打一場網球，但整個
假期中至多打30 場，証明不論他如何安排，必定有
段連續時間恰好打?場(最大)
Ans:
<=小於等於
1<=X1<X2<.....<X21<=30
X1+?<X2+?<...<X21+?<=30+?
We have 21 distinct number X1,X2,...,X21 and
distinct numbers X1+?,X2+?,...,X21+? ,but these
42numbers can take an only 41 different values.
^^^^
30+?=41, ?=11
上述是解答
但我看不懂41怎麼判斷出來的
請高手指點
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