https://codeforces.com/contest/1061/problem/F 题意 假设存在一颗完全k叉树(n<=1e5),允许你进行最多(n*60)次询问,然后输出这棵树的根,每次询问,a,b,c三个点,会返回b是否在a,c之间的路径上 思路 粗略看了下询问次数,可以知道,你最多可以询问60对不同的点,每对点遍历n个点,可以知道n个点在不在这两个点的中间 一开始的思路是,随机找两个点,遍历所有点,然后记录在他们中间的点,在里面再找两个点,继续上述操作,知道剩下一个点,但是假设某一…

https://codeforces.com/contest/1080/problem/F 题意 有k个区间,区间的种类有n种,有m个询问(n,m<=1e5,k<=3e5),每次询问a,b,x,y,代表对于种类编号为[a,b]的每一种区间,是否都存在一个区间x<=l,r<=y,输出yes or no 思路 现将区间按左端点从小到大排序,对于每一个询问首先找出第一个左端点大于x的区间,然后看[a,b]中最大的右端点是否>y即可 需要一颗以种类编号为下标,右端点为权值的主席树,维…

F. Restore a Number   Vasya decided to pass a very large integer n to Kate. First, he wrote that number as a string, then he appended to the right integer k — the number of digits in n. Magically, all the numbers were shuffled in arbitrary order whil…

题意:给你一个数组,求有多少子数组的中位数等于\(m\).(若元素个数为偶数,取中间靠左的为中位数). 题解:由中位数的定义我们知道:若数组中\(<m\)的数有\(x\)个,\(>m\)的数有\(y\)个,只有\(x=y\)或\(y-x\)=1时,中位数才能取到\(m\),记\(m\)在原数组的位置为\(pos\). ​ 于是,我们先遍历\([pos,n]\),记录区间\([pos,i]\)中大于\(m\)的数和小于\(m\)的数个数差,用桶记录差值的个数. 然后我们反着遍历\([1,pos]…

Codeforces Round #485 (Div. 2) F. AND Graph 题目连接: http://codeforces.com/contest/987/problem/F Description You are given a set of size $m$ with integer elements between $0$ and $2^{n}-1$ inclusive. Let's build an undirected graph on these integers in…

Codeforces Round #523 (Div. 2) 题目一览表 来源 考察知识点 完成时间 A Coins cf 贪心(签到题) 2018.11.23 B Views Matter cf 思维??? 2018.11.24 C Multiplicity cf dp 2018.11.27 D TV Shows cf 贪心+multiset 2018.12.2…

Codeforces Round #486 (Div. 3) F. Rain and Umbrellas 题目连接: http://codeforces.com/group/T0ITBvoeEx/contest/988/problem/E Description Polycarp lives on a coordinate line at the point x=0. He goes to his friend that lives at the point x=a. Polycarp can…

题目链接 Codeforces Round #501 (Div. 3) F. Bracket Substring 题解 官方题解 http://codeforces.com/blog/entry/60949 ....看不懂 设dp[i][j][l]表示前i位,左括号-右括号=j,匹配到l了 状态转移,枚举下一个要填的括号,用next数组求状态的l,分别转移 代码 #include<bits/stdc++.h> using namespace std; const int maxn = 207;…

Codeforces Round #499 (Div. 1) F. Tree 题目链接 \(\rm CodeForces\):https://codeforces.com/contest/1010/problem/F Solution 设\(v_i\)表示第\(i\)个点的果子数,设\(b_i=v_i-\sum_{x\in son}v_x\),显然依题意要满足\(b_i\geqslant 0\). 根据差分的性质我们可以得到\(\sum b_i=x\). 假设我们硬点树上剩下了\(m\)个点,则…

Brain's Photos 题目链接: http://codeforces.com/contest/707/problem/A Description Small, but very brave, mouse Brain was not accepted to summer school of young villains. He was upset and decided to postpone his plans of taking over the world, but to becom…