E. Beautiful Subarrays 题目连接: http://www.codeforces.com/contest/665/problem/E Description One day, ZS the Coder wrote down an array of integers a with elements a1,  a2,  ...,  an. A subarray of the array a is a sequence al,  al  +  1,  ...,  ar for so…

E. Beautiful Subarrays   One day, ZS the Coder wrote down an array of integers a with elements a1,  a2,  ...,  an. A subarray of the array a is a sequence al,  al  +  1,  ...,  ar for some integers (l,  r) such that 1  ≤  l  ≤  r  ≤  n. ZS the Coder…

链接:http://codeforces.com/contest/665/problem/E 题意:求规模为1e6数组中,连续子串xor值大于等于k值的子串数: 思路:xor为和模2的性质,所以先预处理之后,可以枚举这种确实子串区间的方法为O(n^2): 优化?把每一个前缀xor扔到二叉树中,从根节点出发,以高位前缀值的二进制数构造一颗二叉树,这样就可以在构造的时候,实现对子树节点个数的求解:之后在线求解到当前节点的可选的前缀xor的个数, 即以k为主线 如果当前位k为1,则在前缀二叉树中只能找…

先转换成异或前缀和,变成询问两个数异或≥k的方案数. 分治然后Trie树即可. #include<cstdio> #include<algorithm> #define N 1000010 #define mid (l+r>>1) #define ll long long using namespace std; int n,k,a[N];ll ans; struct Trie { ][],tot,sum[N*]; void init() { ;i<=tot;i+…

Educational Codeforces Round 63 (Rated for Div. 2) D. Beautiful Array time limit per test 2 seconds memory limit per test 256 megabytes input standard input output standard output You are given an array aa consisting of nn integers. Beauty of array i…

题目链接:http://codeforces.com/problemset/problem/665/E (http://www.fjutacm.com/Problem.jsp?pid=2255) 题意:找出有多少个连续的区间[l,r](1  ≤  l  ≤  r  ≤  n),该区间中所有的数的异或值大于等于k: 思路:首先,如果是单看题目的话,会发现暴力的话复杂度是O(n^3),但是我们先预处理异或前缀和,然后你会发现[l,r]区间的异或和等于s[l-1]^s[r],这样就可以O(n^2)的求…

http://codeforces.com/contest/665/problem/E 给定一个序列,问其中有多少个区间,所有数字异或起来 >= k 看到异或,就应该想到异或的性质,A^B^B = A,所以,用sum[i]表示1--i的异或值,那么i...j的异或值就是sum[j] ^ sum[i - 1] 所以原问题转化为在一个数组中,任选两个数,异或值 >= k 首先所有数字 <= 1e9 那么前缀异或值 <= 2^31 - 1 那么用int就够了,从30位开始插入字典树,(1…

D. Beautiful Array time limit per test 2 seconds memory limit per test 256 megabytes input standard input output standard output You are given an array aa consisting of nn integers. Beauty of array is the maximum sum of some consecutive subarray of t…

F. Four Divisors 题目连接: http://www.codeforces.com/contest/665/problem/F Description If an integer a is divisible by another integer b, then b is called the divisor of a. For example: 12 has positive 6 divisors. They are 1, 2, 3, 4, 6 and 12. Let's def…

D. Simple Subset 题目连接: http://www.codeforces.com/contest/665/problem/D Description A tuple of positive integers {x1, x2, ..., xk} is called simple if for all pairs of positive integers (i,  j) (1  ≤ i  <  j ≤ k), xi  +  xj is a prime. You are given a…