题目链接: http://codeforces.com/problemset/problem/645/B 题意: 给定步数和排列,每步可以交换两个数,问最后逆序数最多是多少对? 分析: 看例子就能看出来肯定是不断往中间逼近,然后交换头尾两个,给定交换的对数,直接算就好了,复杂度O(1) 代码: #include<iostream> using namespace std; typedef long long ll; int main (void) { ll n, m; cin>>n…
简单题. 第一次交换$1$和$n$,第二次交换$2$和$n-1$,第三次交换$3$和$n-2$.....计算一下就可以了. #pragma comment(linker, "/STACK:1024000000,1024000000") #include<cstdio> #include<cstring> #include<cmath> #include<algorithm> #include<vector> #include&…
It is a balmy spring afternoon, and Farmer John's n cows are ruminating about link-cut cacti in their stalls. The cows, labeled 1 through n, are arranged so that the i-th cow occupies the i-th stall from the left. However, Elsie, after realizing that…
题目链接: B. Mischievous Mess Makers time limit per test 1 second memory limit per test 256 megabytes input standard input output standard output It is a balmy spring afternoon, and Farmer John's n cows are ruminating about link-cut cacti in their stalls…
B. Mischievous Mess Makers 题目连接: http://www.codeforces.com/contest/655/problem/B Description It is a balmy spring afternoon, and Farmer John's n cows are ruminating about link-cut cacti in their stalls. The cows, labeled 1 through n, are arranged so…
Crossings Time Limit: 20 Sec Memory Limit: 256 MB 题目连接 http://codeforces.com/gym/100463 Description Given a permutation P of {0, 1, ..., n − 1}, we define the crossing number of it as follows. Write the sequence 0, 1, 2, . . . , n − 1 from left to ri…
题目链接:http://codeforces.com/contest/459/problem/D D. Pashmak and Parmida's problem time limit per test 3 seconds memory limit per test 256 megabytes input standard input output standard output Parmida is a clever girl and she wants to participate in O…
题目链接 题意:给出数组A,定义f(l,r,x)为A[]的下标l到r之间,等于x的元素数.i和j符合f(1,i,a[i])>f(j,n,a[j]),求i和j的种类数. 我们可以用map预处理出 f(1, i, a[i]) 和 f(j, n, a[j]) ,记为s1[n], s2[n]. 这样就变成求满足 s1[i] > s[j], i < j 情况的数量了,你会发现跟求逆序对一样 分析: 做题的时候想到过逆序数,但是很快放弃了,还是理解不深刻吧,,,233. 看了这个博客以后才明白这些过…
                                                                E. Infinite Inversions                                                                                          time limit per test 2 seconds                                            …
http://codeforces.com/problemset/problem/61/E 题意是求 i<j<k && a[i]>a[j]>a[k] 的对数 会树状数组求逆序数的话,这个推一下就能出结果: 做法: 1.离散化,由于a[i]能够达到1e9 2.插入a[i]的时候,记录x[i]=i-sum(a[i]); a[i]之前比a[i]大的有x[i]个 3.插入完毕后,求a[i] 之后比a[i]小的数的个数y[i] ans=segma(x[i]*y[i])   注…