https://codeforces.com/contest/1157/problem/F

题意：求一个相邻元素之间绝对值为小于1的最大环

题解：

1、桶排序；

2、环肯定在没有或者数量为1的元素之间；

/*
*@Author:   STZG
*@Language: C++
*/
#include <bits/stdc++.h>
#include<iostream>
#include<algorithm>
#include<cstdlib>
#include<cstring>
#include<cstdio>
#include<string>
#include<vector>
#include<bitset>
#include<queue>
#include<deque>
#include<stack>
#include<cmath>
#include<list>
#include<map>
#include<set>
//#define DEBUG
#define RI register int
#define endl "\n"
using namespace std;
typedef long long ll;
//typedef __int128 lll;
const int N=200000+10;
const int M=100000+10;
const int MOD=1e9+7;
const double PI = acos(-1.0);
const double EXP = 1E-8;
const int INF = 0x3f3f3f3f;
int t,n,m,k,p,l,r,u,v;
int ans,cnt,flag,temp,sum;
int a[N],b[N],c[N];
char str;
struct node{};
int main()
{
#ifdef DEBUG
	freopen("input.in", "r", stdin);
	//freopen("output.out", "w", stdout);
#endif
    //ios::sync_with_stdio(false);
    //cin.tie(0);
    //cout.tie(0);
    //scanf("%d",&t);
    //while(t--){
    scanf("%d",&n);
    for(int i=1;i<=n;i++){
        scanf("%d",&a[i]);
        b[a[i]]++;
    }
    l=0;
    r=0;
    temp=0;
    ans=0;
    int L=0,R=0;
    for(int i=1;i<=200000;i++){
        if(b[i]){
            //cout<<i<<endl;
            if(b[i]>=2){
                temp+=b[i];
                r++;
            }else{
                temp+=b[i];
                if(temp>ans){
                    L=l;
                    R=i;
                    ans=temp;
                }
                l=i;
                r=i;
                temp=b[i];
            }
        }else{
            temp+=b[i];
            if(temp>ans){
                L=l;
                R=i;
                ans=temp;
            }
            l=i;
            r=i;
            temp=b[i];
        }
    }
    if(temp>ans){
        L=l;
        R=n+1;
        ans=temp;
    }
    //cout<<L<<" "<<R<<endl;
    while(b[L])c[++cnt]=L,b[L]--;
    for(int i=L+1;i<R;i++){
        for(int j=1;j<=(b[i]+1)/2;j++){
            c[++cnt]=i;
        }
    }
    while(b[R])c[++cnt]=R,b[R]--;
    for(int i=R-1;i>L;i--){
        for(int j=1;j<=b[i]/2;j++){
            c[++cnt]=i;
        }
    }
    cout<<cnt<<endl;
    for(int i=1;i<=cnt;i++)
        printf("%d%c",c[i]," \n"[i==cnt]);
    //}

#ifdef DEBUG
	printf("Time cost : %lf s\n",(double)clock()/CLOCKS_PER_SEC);
#endif
    //cout << "Hello world!" << endl;
    return 0;
}