【样例1】
6
1 4 4 7 4 1
【样例2】
4
1 3 3 7
【样例1】
3
【样例2】
-1
//终于成功了
#include <cmath>
#include <iostream>
#include <algorithm>
using namespace std;
const int N = 110;
int n;
int a[N], b[N];
int main(){
cin >> n;
for (int i = 1; i <= n; i ++ ) cin >> a[i];
sort(a + 1, a + 1 + n);
for (int i = 1; i <= n; i ++ ) {
b[a[i]] ++;
}
int t = 0;
int d[N];
for (int i = 1; i <= 101; i ++ ){
if (b[i] != 0) d[++ t] = i;
}
if (t == 1) cout << 0 << endl;
else if (t == 2) cout << d[2] - d[1] << endl;
else if (t == 3) {
if (d[1] + d[3] == 2 * d[2]) cout << d[3] - d[2] << endl;
else cout << "-1" << endl;
}
else cout << "-1" << endl;
return 0;
}
//不知道那里错了，但是只有八十分，有哪位大神可以指出来吗
#include <cmath>
#include <iostream>
using namespace std;
const int N = 110;
int n;
int a[N];
int main(){
cin >> n;
for (int i = 0; i < n; i ++ ) cin >> a[i];
int minn = 111, maxn = 0;
for (int i = 0; i < n; i ++ ){
minn = min(minn, a[i]);
maxn = max(maxn, a[i]);
}
int x = maxn + minn >> 1;
int y = maxn - x;
bool t = true;
for (int i = 0; i < n; i ++ ){
if (abs(a[i] - x) != 0 && abs(a[i] - x) != y)
t = false;
}
if (t) cout << y << endl;
else cout << "-1" << endl;
return 0;
}
原文：https://www.cnblogs.com/Iamcookieandyou/p/13110262.html