10.19 Question record

Overview

The total difficulty of completing cf: $2000+2300+2000+2300+1200+2000+2800+2400+1800+2200=21000$

Be wyq $\approx 20000$ Hanging

Brief solution

CF920F

Simple ds problem, the method is similar to the square root of the interval. There are no more operations for each number. So we maintain the interval sum and interval $\max$ . If the interval$\max \le 2$ Then there is no need to modify it. And we only need$O(x\ln x)$ preprocessing$D\left(X\right)$ can

CF785D

First, we consider for each (separately calculate the contribution, consider this before $n$ th(behind$m$ a), then for this(contribution is,$\sum _{i=1}^{\min (n,m)}{C}_{n-1}^{i-1}\times C_m^i$. Then by looking at the solution, we know that this is equivalent to $C_{n+m-1}^n$。

CF353D

The idea of ​​this topic is similar to CF622E. We consider setting $f_i$Indicates to the $i$ Individuals need to exchange at least several times (before guarantee$i$ operations have been arranged and completed). Then$f_i=\max (f_{i-1}+[i-lto\le gs-1],i-gs)$ , where$LA$ represents the lastFto appear,$GS$ represents the currentlyFnumber. Time complexity$O\left(n\right)$

CF79D

This topic is quite easy to write after thinking about it. We consider XOR difference, assuming $n$ state of a lamp is1011then as soon as the difference11101. So suppose we flip$[l,r]$ This interval is equivalent tocfl cf_{l} of thedifference array$c{f}_l$Sum $c{f}_{r+1}$ Just go and flip.

Differential array 1number of affirmative $\le 20$ . So we consider state pressure dp. Let$f_i$Indicates arrival status iiMinimum number of operations of$i$ , state$i$ if the$j$ bit is$1\; is$ equivalent to puttingjjThe minimum number of times$j$ lights are turned on. The transfer is simple$f_i=\underset{A\in i,B\in i}{\mathrm{me}}(f_{i\oplus A\oplus B}+g_{A,B})$，$g_{i,j}$Represents $[i,j]$ interval except$i,j$ The minimum number of times that the state changes and the rest does not change state. This can be preprocessed with bfs.

CF1369E

We consider everyone to choose all, if there is still a food that has not been eaten, then people with this item will definitely not eat Leo. So we put the person who owns those foods to the end, make up for another dish he requested, and keep doing the same operations until there are no more dishes.

CF590C

01bfs template question, because there are only 3 kinds of countries. So we remember $d_{k=[1/2/3],i,j}$It represents $k$ country to$(i,j)$ Shortest distance. Immediately${\min }_{i,j}(d_{0,i,j}+d_{1,i,j}+d_{2,i,j}-2\times [a_{i,j}=$.$])$。

01bfs General processing edge rights $[0,1]$ bfs. Take the first element of the team each time, and put it at the head of the team if it is the same level for each operation that can be relaxed, otherwise put it at the end of the team.