A. difficult to graph theory
Meaning of the questions:
Given consisting of n-$ $ $ m $ points and edges undirected FIG requires a selected number of edges. An edge is selected if and only if it happens to be a simple loop through.
A ring is known as a simple ring, if and only if all the points on the ring is only after a time in this loop.
These side output number and XOR. Side from $ 1 $ numbering.
$ 1 \ n \ 10 ^ 6 \; 1 \ m \ min the \ {10 ^ 6, n \ times (n + 1) / 2 \} $.
analysis:
Note: There may be a much simpler view of the ring, questions asked on all sides to select a simple ring. It is the examination room I made a mistake. (In fact, I got it right, is also likely to draw up ......)
Cluck
achieve:
Cluck
summary:
Cluck
B.Book
Meaning of the questions:
Define a valid sequence of length $ N $, the first known as X-$ $, beginning from the second one to increase than the previous $ A $, or a decrease over the previous $ B $.
Seeking a legitimate any sequence, and all the elements of exactly $ M $.
Enter assurance answer exists.
$ 1 \ n \ 10 ^ 5 \; | x | \ 10 ^ 6 \; 1 \ the A, B, \ the $ 10 ^ 6.
analysis:
Cluck
achieve:
Cluck
summary:
Cluck
C. Internet
Meaning of the questions:
A length of a sequence $ N $ $ a \ {n \} $, $ a_i \ in [1,10 ^ 9] $. Known locations $ s $ $ a_ {p_i} = d_i $.
$ M $ another set conditions, each section gives a $ [l_i, r_i] $, and inform this interval has $ $ K_i elements, their values are strictly greater than $ [l_i, r_i] $ in other $ r_i-l_i + 1-k_i $ elements.
$ N \ 10 ^ 5 \; m \ 2 \ Times 10 ^ 5 \; \ sum k_i \ 3 \ Times 10 ^ 5 $.
analysis:
Cluck
achieve:
Cluck
summary:
Cluck
Day Summary:
T1 wrong meaning of the questions, sentenced to a tree ring (pseudo), was $ 40pts $ good results.
T2 came up with a false greedy, he won the $ 70pts $ good results.
T3 think of topological sorting, but I did not expect even the tree line optimization side, $ RE $ $ 10pts $ obtain good results.
Water failure! (Plan through .jpg)
T1 obviously I'm not familiar series of questions $ Tarjan $ algorithm derived, which is difficult to glimpse the right path.
T2在讨论的时候，有人一直在喊：“这题只配放在普及组”。考出来也确实是人均$AC$，被我浪掉$30pts$。
T3其实很$naive$的线段树优化连边思想，$\mathscr{Pedesis}$谈到他一秒想到正解，奈何实现起来细节太多才痛失$AC$。
如何思想$Sharpen$？
一是理解透彻所有算法的思想内核，提升上限；
二是多练多想多总结，刷熟练度增强联想能力，提升下限。
$methed2$同时也是磨炼码力的途径。脑和手，对应着建模和实现，是$OI$的两大维度。两者互相牵制又促进，同时发展，能力均衡。
这是不是有点像发表遗言……不太吉利，不说了。