C 解法, 执行用时: 1ms, 内存消耗: 368KB, 提交时间: 2019-04-26

#include<stdio.h>
void paixu(int *a,int n)
{
    int i,j,t;
    for(i=0;i<n;i++)
        for(j=i+1;j<n;j++)
            if(a[i]>a[j])
            {
                t=a[i];
                a[i]=a[j];
                a[j]=t;
            }
}
int main()
{
    int i,d,n,flag=1,x[1000];
    scanf("%d\n",&n);
    for(i=0;i<n;i++)
        scanf("%d",&x[i]);
    paixu(x,n);
    d=x[1]-x[0];
    for(i=1;i<n;i++)
        if(x[i]-x[i-1]!=d)
        {
            flag=0;
            break;
        }
    if(flag)
        printf("Possible\n");
    else
        printf("Impossible\n");
}

C++ 解法, 执行用时: 1ms, 内存消耗: 368KB, 提交时间: 2017-08-13

#include <iostream>
#include <string>
#include <set>
#include <climits>
using namespace std;

int main() {
    int n, d;
    int a, a_1 = INT_MAX, a_n = INT_MIN;
    int sum = 0;
    set<int> s;
    cin >> n;
    while (cin >> a) {
        a_1 = min(a, a_1);
        a_n = max(a, a_n);
        sum += a;
        s.insert(a);
    }
    if ((a_n - a_1) % (n - 1) != 0)
        cout << "Impossible" << endl;
    else {
        d = (a_n - a_1) / (n - 1);
        if ((2 * a_1 + (n - 1) * d) * n != 2 * sum)
            cout << "Impossible" << endl;
        else {
            for (int i = 1; i < n - 1; i++) {
                if (s.find(a_1 + (n - 1) * d) == s.end()) {
                    cout << "Impossible" << endl;
                    return 0;
                }
            }
            cout << "Possible" << endl;
        }
    }
    return 0;
}