CodeForces 382C【模拟】

活生生打成了大模拟。。。

#include <bits/stdc++.h>
using namespace std;
typedef long long LL;
typedef unsigned long long ULL;
typedef pair<int,int>PII;
const double eps=1e-5;
const double pi=acos(-1.0);
//const int mod=1e9+7;
const int INF=0x3f3f3f3f;
//http://codeforces.com/contest/382/submission/22599025

const int N=1e5+10;
int a[N];
int ans[N],num;
int n;

void shuchu()
{
    sort(ans,ans+num);
    int e=unique(ans,ans+num)-ans;
    printf("%d\n",e);
    for(int i=0; i<e; i++)
        printf("%d ",ans[i]);
}

map<int,int>mp;
int mp_num;

int main()
{
    scanf("%d",&n);
    for(int i=1; i<=n; i++)
        scanf("%d",&a[i]);

    sort(a+1,a+1+n);

    if(n==1)
    {
        puts("-1");
        return 0;
    }
    if(n==2)
    {
        int d=a[n]-a[n-1];
        if(d%2==1)
        {
            num=0;
            ans[num++]=a[n-1]-d;
            ans[num++]=a[n]+d;
            shuchu();
        }
        else
        {
            num=0;
            ans[num++]=a[n-1]-d;
            ans[num++]=a[n]-d/2;
            ans[num++]=a[n]+d;
            shuchu();
        }
        return 0;
    }
    //3 4 4 5
    //1 2 3
    //1 2 4
    int d1,temp,d2,num1,num2;
    int dx1,dx2;
    num2=num1=0;
    d1=a[2]-a[1];
    dx1=2;
    num1++;
    mp_num=1;
    mp[d1]=1;
    for(int i=3; i<=n; i++)
    {
        temp=a[i]-a[i-1];
        if(!mp[temp])
        {
            mp[temp]=1;
            mp_num++;
        }
        if(temp!=d1)
        {
            num2++;
            dx2=i;
            d2=temp;
        }
        else
            num1++;
    }
    if(mp_num>=3)
    {
        puts("0");
        return 0;
    }
    if(!num2)
    {
        num=0;
        ans[num++]=a[1]-d1;
        ans[num++]=a[n]+d1;
        shuchu();
    }
    else
    {
        if(num1==1&&num2==1)
        {
            int res=a[dx2]-d1;
            if(res*2==(a[dx2]+a[dx2-1]))
            {
                puts("1");
                printf("%d\n",res);
                return 0;
            }
            res=a[dx1]-d2;
            if(res*2==(a[dx1]+a[dx1-1]))
            {
                puts("1");
                printf("%d\n",a[dx1]-d2);
                return 0;
            }
            puts("0");
        }
        else if(num2==1)
        {
            int res=a[dx2]-d1;
            if(res*2==(a[dx2]+a[dx2-1]))
            {
                puts("1");
                printf("%d\n",res);
            }
            else
                puts("0");
        }
        else if(num1==1)
        {
            int res=a[dx1]-d2;
            if(res*2==(a[dx1]+a[dx1-1]))
            {
                puts("1");
                printf("%d\n",a[dx1]-d2);
            }
            else
                puts("0");
        }
        else
            puts("0");
    }
    return 0;
}