codeforces 877C

题目链接：

http://codeforces.com/contest/877/problem/C

题解：

规律题。

代码：

#include <map>#include <cmath>#include <string>#include <vector>#include <cstdio>#include <cstring>#include <iostream>#include <algorithm>using namespace std;#define met(a,b) memset(a,b,sizeof(a))#define inf 0x3f3f3f3fvector<int>p1,p2;int main(){    int n;    scanf("%d",&n);    for(int i=1;i<=n;i++)    {        if(i%2)            p1.push_back(i);        else            p2.push_back(i);    }    int m=(int)(p1.size()+p2.size()*2);    printf("%d\n",m);    for(int i=0;i<p2.size();i++)        printf("%d ",p2[i]);    for(int i=0;i<p1.size();i++)        printf("%d ",p1[i]);    for(int i=0;i<p2.size();i++)        printf("%d ",p2[i]);    printf("\n");}