AT4255 [ABC109C] Skip

每座城市 $\large p_i$ 距离起点位置为 $\lvert p_i-x \lvert$，$d$ 满足题意时当且仅当 $d \,\,|\,\, |p_i-x|(i=1,2,3,……,n)$。若要 $d$ 尽量大，则是求 $\gcd(|p_1-x|,|p_2-x|,……,|p_n-x|)$。

代码：

#include <bits/stdc++.h>
using namespace std;

#define int long long

const int N = 1e5 + 5;
int p[N];

int gcd(int a, int b)
{
	if (b == 0) return a;
	return gcd(b, a % b);
}

signed main()
{
	int n, x, gcdx = 1;
	scanf("%lld %lld %lld", &n, &x, &p[1]);
	p[1] -= x;
	gcdx = p[1];
	for (int i = 2; i <= n; i++)
	{
		scanf("%lld", &p[i]);
		p[i] -= x;
		gcdx = gcd(gcdx, p[i]); 
	}
	printf("%lld\n", abs(gcdx));
	return 0;
}