## 202006-2 sparse vector

subject
Sparse vector
Title screenshot:
![image-20211201234641418](C:\Users\long yongcheng\AppData\Roaming\Typora\typora-user-images\image-20211201234641418.png)
thinking
60 point answer
My first idea is to open a two-dimensional array, which is equivalent to opening a two-dimensional table with two rows and many columns (why do you say many co ...

Posted by **ducey** on *Fri, 03 Dec 2021 07:16:54 -0800*

## CCF 2021-09-2 non zero segment division

Title Description
A1,A2,⋯,An It's a n An array of natural numbers (non negative integers). We call it Ai,⋯,Aj Is a non-zero segment if and only if the following conditions are met at the same time:
1≤i≤j≤n；For any integer k. If i ≤ K ≤ j, then Ak>0；i=1 or Ai&m ...

Posted by **davo666** on *Sun, 10 Oct 2021 05:29:58 -0700*

## CCF201709-2 public key box

Title: public key box Problem description
In one school, teachers share N classrooms. According to the regulations, all keys must be placed in the public key box. Teachers cannot take keys home. Every time before class, the teacher finds the key of his classroom from the public key box to open the door. After class, he puts the key back in the ...

Posted by **ipruthi** on *Sat, 11 Sep 2021 18:59:15 -0700*