[CF 612E]Square Root of Permutation
A permutation of length n is an array containing each integer from 1 to n exactly once. For example, q = [4, 5, 1, 2, 3] is a permutation. For the permutation q the square of permutation is the permutation p that p[i] = q[q[i]] for each i = 1... n. For example, the square of q = [4, 5, 1, 2, 3] is p = q2 = [2, 3, 4, 5, 1].
This problem is about the inverse operation: given the permutation p you task is to find such permutation q that q2 = p. If there are several such q find any of them.
Input
The first line contains integer n (1 ≤ n ≤ 106) — the number of elements in permutation p.
The second line contains n distinct integers p1, p2, ..., pn (1 ≤ pi ≤ n) — the elements of permutation p.
Output
If there is no permutation q such that q2 = p print the number "-1".
If the answer exists print it. The only line should contain n different integers qi (1 ≤ qi ≤ n) — the elements of the permutation q. If there are several solutions print any of them.
Examples
input
4
2 1 4 3
output
3 4 2 1
input
4
2 1 3 4
output
-1
input
5
2 3 4 5 1
output
4 5 1 2 3
题目大意:
给你个置换p,然后做平方运算,得到置换q,题目给你q,问你能否找到p,要构造出来。
题解:
这道题要求倒推出一个置换,由于原置换p中的环不一定全是奇数环,所以平方之后有可能有环会裂开。
对于平方后的置换q中的奇数环,直接在里面推。偶数环就看是否有相同大小的偶数环与它合并。
//Never forget why you start
#include<iostream>
#include<cstdio>
#include<cstdlib>
#include<cstring>
#include<cmath>
#include<algorithm>
#include<vector>
using namespace std;
int n,m,a[],lm,ans[],q[];
struct node{
int sum;
vector<int>p;
friend bool operator < (const node a,const node b){
return a.sum<b.sum;
}
}s[];
int vis[],cnt;
void dfs(int r){
vis[r]=;
cnt++;
s[lm].p.push_back(r);
if(vis[a[r]])return;
else dfs(a[r]);
}
int main(){
int i,j;
scanf("%d",&n);
for(i=;i<=n;i++)scanf("%d",&a[i]);
for(i=;i<=n;i++)
if(!vis[i]){
cnt=;
lm++;
dfs(i);
s[lm].sum=cnt;
}
sort(s+,s+lm+);
bool flag=;
for(i=;i<=lm;i++){
if(s[i].sum&)continue;
else{
if(s[i+].sum==s[i].sum){i++;continue;}
else {flag=;break;}
}
}
if(flag){printf("-1\n");return ;}
for(i=;i<=lm;i++){
if(s[i].sum&){
for(j=;j<s[i].sum;j++)
q[j*%s[i].sum]=s[i].p[j];
for(j=;j<s[i].sum-;j++)
ans[q[j]]=q[j+];
ans[q[s[i].sum-]]=q[];
}
else{
int k=i+;
for(j=;j<s[i].sum;j++){
ans[s[i].p[j]]=s[k].p[j];
ans[s[k].p[j]]=s[i].p[(j+)%s[i].sum];
}
i++;
}
}
for(i=;i<=n;i++)
printf("%d ",ans[i]);
return ;
}
[CF 612E]Square Root of Permutation的更多相关文章
- Codeforces 612E - Square Root of Permutation
E. Square Root of Permutation A permutation of length n is an array containing each integer from 1 t ...
- codefroces 612E Square Root of Permutation
A permutation of length n is an array containing each integer from 1 to n exactly once. For example, ...
- Codeforces.612E.Square Root of Permutation(构造)
题目链接 \(Description\) 给定一个\(n\)的排列\(p_i\),求一个排列\(q_i\),使得对于任意\(1\leq i\leq n\),\(q_{q_i}=p_i\).无解输出\( ...
- Square Root of Permutation - CF612E
Description A permutation of length n is an array containing each integer from 1 to n exactly once. ...
- CF612E Square Root of Permutation
题目分析 我们首先模拟一下题意 假设有一个 \(q _1\) \(p\) \(a_1\) \(a_x\) \(a_{a_1}\) \(a_{a_x}\) \(q\) \(x\) \(a_1\) \(a ...
- Codeforces 715A. Plus and Square Root[数学构造]
A. Plus and Square Root time limit per test 2 seconds memory limit per test 256 megabytes input stan ...
- Project Euler 80:Square root digital expansion 平方根数字展开
Square root digital expansion It is well known that if the square root of a natural number is not an ...
- Codeforces 715A & 716C Plus and Square Root【数学规律】 (Codeforces Round #372 (Div. 2))
C. Plus and Square Root time limit per test 2 seconds memory limit per test 256 megabytes input stan ...
- (Problem 57)Square root convergents
It is possible to show that the square root of two can be expressed as an infinite continued fractio ...
随机推荐
- UINavigationController + UIScrollView组合,视图尺寸的设置探秘(一)
UINavigationController和UIScrollView是iOS下几种主要的交互元素,但当我搭配二者在一起时,UIScrollView的滚动区域出现了很诡异的现象.我希望UIScroll ...
- 51nod 1350 斐波那契表示(递推+找规律)
传送门 题意 分析 我们发现该数列遵循下列规律: 1 1,2 1,2,2 1,2,2,2,3 1,2,2,2,3,2,3,3 我们令A[i]表示f[i]开始长为f[i-1]的i的最短表示和 那么得到A ...
- THINKPHP 框架的模板技术
//echo C('name'); App/Action/IndexAction.class.php文件夹下的 URL模式 //输出URL模式//echo C('URL_MODEL'),'<br ...
- Java基础之Java编译运行过程
Java编译运行过程 程序员所编写的是以.java为后缀的文件,此文件操作系统不能正确识别,因此,首先要经过编译,生成所谓的字节码文件(.class),而字节码文件需要JVM来提供运行环境的支持. J ...
- 老男孩Day4作业:员工信息查询系统
1.作业需求: (1).工信息表程序,实现增删改查操作: (2).可进行模糊查询,语法至少支持下面3种: select name,age from staff_table where ...
- UVA10173 Smallest Bounding Rectangle 最小面积矩形覆盖
\(\color{#0066ff}{题目描述}\) 给定n(>0)二维点的笛卡尔坐标,编写一个程序,计算其最小边界矩形的面积(包含所有给定点的最小矩形). 输入文件可以包含多个测试样例.每个测试 ...
- linux下的静态库和动态库
一.linux下的静态库 静态库中的被调用的函数的代码会在编译时一起被复制到可执行文件中去的!!可执行文件在运行不需要静态库的存在! 二.linux下动态库的构建和使用 1.动态库的构建 ...
- [POI2014]KUR-Couriers BZOJ3524 主席树
给一个长度为n的序列a.1≤a[i]≤n. m组询问,每次询问一个区间[l,r],是否存在一个数在[l,r]中出现的次数大于(r-l+1)/2.如果存在,输出这个数,否则输出0. Input 第一行两 ...
- Android layout布局属性、标签属性总结大全
RelativeLayout 第一类:属性值为true可false android:layout_centerHrizontal 水平居中 android:layout_centerVe ...
- python 对三维CT数据缩放
项目需要对CT数据进行缩放,这里我存储CT数据的格式是numpy数组. 一共尝试了三种方法,分别是numpy.resize,cv2.resize,scipy.ndimage.interpolation ...