2021.07.12 [NOIP improves Group B] Simulation summary

Good elements

Naked Hash (I am a paratrooper , I can do this wrong)

The general idea of ​​the topic

If there exists Am + An + Ap = Ai (1 <= m, n, p < i) (m, n, p can be the same), Ai is a "good element"

Um? That's it? ? How many "good elements" are there? ? ?

answer

Move an item Am + An = Ai -
The hash on the left side of Ap is stored, and the n ² enumeration
hash on the right side is the single hash I typed during the exam, RTE?
Make it a little bigger, TLE? ?
Change to double hashing, WA? ? ?
Change mod, AC! ! !

shortest path

I never thought about DP, wu...

The general idea of ​​the topic

Select several points from n points (must select $b1$ , cannot choose$b2$ ), from 0 ~ n -1 in order, and then use other points from n-1 ~ 0 to find the shortest path.

answer

The DP
conversion question means that two people walking cannot walk to the same point.
Let $f\left[i\right]\left[j\right]$ is the first person in i and the second person in j.
Let$k=max(i,j)$ , then it must also be satisfied that 1~k have all been passed.
Then$f\left[i\right]\left[j\right]$ can be transferred to$f[k+1]\left[j\right]$ and$f[i][k+1]$
Special judgment$k==n$ and$b1$，$b2$ case l,.

longest common substring

Double pointer.

Vani and Cl2 hide and seek

The longest anti-strand length of DAG.