HDU 5916 Harmonic Value Description 【构造】(2016中国大学生程序设计竞赛(长春))

Harmonic Value Description

Time Limit: 2000/1000 MS (Java/Others)    Memory Limit: 65536/65536 K (Java/Others)

Total Submission(s): 3    Accepted Submission(s): 3

Special Judge

Problem Description

The harmonic value of the permutation p1,p2,⋯pn is

∑i=1n−1gcd(pi.pi+1)

Mr. Frog is wondering about the permutation whose harmonic value is the strictly k-th smallest among all the permutations of [n].

 

Input

The first line contains only one integer T (1≤T≤100), which indicates the number of test cases.

For each test case, there is only one line describing the given integers n and k (1≤2k≤n≤10000).

 

Output

For each test case, output one line “Case #x: p1 p2 ⋯ pn”, where x is the case number (starting from 1) and p1 p2 ⋯ pn is the answer.

 

Sample Input

24 14 2

 

Sample Output

Case #1: 4 1 3 2Case #2: 2 4 1 3

 

Source

2016中国大学生程序设计竞赛（长春）-重现赛

 

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题目链接：

　　http://acm.hdu.edu.cn/showproblem.php?pid=5916

题目大意：

　　给你N和K（1<=K<2K<=2N），求一个1~2N的排列，使得∑gcd(A_i,A_i+1)恰为第K小（等视为相同小）。

题目思路：

　　【构造】

　　这题一看2K<=2N，可能就是构造题。如果1,2,3...2N排列的话∑gcd(A_i,A_i+1)为第1小。

　　若要∑gcd(A_i,A_i+1)=K，只需要将2K和K提出来，将2K放在开头，K放在第二个，接下来只要满足相邻两个数仍然相差1即可。

　　只要将K-1~1接在K后面，把K+1~2N接在1后面，去掉2K即可。（2K-1，2K+1为奇数，gcd=1）

////by coolxxx//#include<bits/stdc++.h>#include<iostream>#include<algorithm>#include<string>#include<iomanip>#include<map>#include<stack>#include<queue>#include<set>#include<bitset>#include<memory.h>#include<time.h>#include<stdio.h>#include<stdlib.h>#include<string.h>//#include<stdbool.h>#include<math.h>#define min(a,b) ((a)<(b)?(a):(b))#define max(a,b) ((a)>(b)?(a):(b))#define abs(a) ((a)>0?(a):(-(a)))#define lowbit(a) (a&(-a))#define sqr(a) ((a)*(a))#define swap(a,b) ((a)^=(b),(b)^=(a),(a)^=(b))#define mem(a,b) memset(a,b,sizeof(a))#define eps (1e-10)#define J 10000#define mod 1000000007#define MAX 0x7f7f7f7f#define PI 3.14159265358979323#pragma comment(linker,"/STACK:1024000000,1024000000")#define N 104using namespace std;typedef long long LL;double anss;LL aans,sum;int cas,cass;int n,m,lll,ans;int main(){#ifndef ONLINE_JUDGEW//freopen("1.txt","r",stdin);//freopen("2.txt","w",stdout);#endifint i,j,k;//init();//for(scanf("%d",&cass);cass;cass--)for(scanf("%d",&cas),cass=1;cass<=cas;cass++)//while(~scanf("%s",s))//while(~scanf("%d",&n)){scanf("%d%d",&n,&m);printf("Case #%d: ",cass);printf("%d %d",m+m,m);for(i=m-1;i;i--)printf(" %d",i);for(i=m+1;i<=n;i++)if(i!=m+m)printf(" %d",i);puts("");}return 0;}/*////*/