Codeforces Round #442 (Div. 2) C. Slava and tanks 【找规律】

分成三组
第一组是2 4 6 …
第二组是1 3 5 …
第三组是2 4 6 …

#include <stdio.h>#include <string.h>#include <iostream>#include <algorithm>#include <vector>#include <queue>#include <set>#include <map>#include <string>#include <math.h>#include <stdlib.h>#include <time.h>using namespace std;vector<int>ans;int main(){    //freopen("in.txt","r",stdin);    //freopen("out.txt","w",stdout);    int n;    scanf("%d",&n);    for(int i=2;i<=n;i+=2) ans.push_back(i);    for(int i=1;i<=n;i+=2) ans.push_back(i);    for(int i=2;i<=n;i+=2) ans.push_back(i);    printf("%d\n",ans.size());    for(int i=0;i<ans.size();i++) cout<<ans[i]<<" ";    return 0;