前言：一开始看到数据量这么大，我怎么拆分出因子，看了题解才发现要大减枝，但是如何拆分因数我还是要好好学一下

$10^{18}$ 的拆分因子有 $10^5$ 的复杂度，再乘以 $10^3$ 的数量，加上我们的大减枝刚刚好过关

题目地址

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

#define int long long
int t;
int n;
const int N = (int)1e3+5;
int a[N];
int dis[N];

vector<int> fun(int x){
	vector<int> e;
	int i = 1;
	while(i*i<=x&&i<=n){
		if(x%i==0){
			e.push_back(i);
			if(i!=x/i){
				if(x/i<=n) e.push_back(x/i);
			}
		}
		i++;
	}
	return e;
}

signed main(){
	cin >> n;
	for(int i=1;i<=n;i++){
		cin >> a[i];
		dis[i] = INT_MAX;
	}
	dis[1] = 0;
	queue<int> q;
	q.push(1);
	while(q.size()){
		int u = q.front(); q.pop();
		vector<int> e = fun(a[u]);
		//cout << " u " << u << endl;

		for(auto v:e){
			//cout << " 因子有 " << v << endl;
			if(u+v<=n&&dis[u]+1<dis[u+v]){
				dis[u+v] = dis[u] + 1; q.push(u+v);
			}
			if(u-v>0&&dis[u]+1<dis[u-v]){
				dis[u+v] = dis[u] + 1; q.push(u-v);
			}
		}
	}
	cout << dis[n];
	return 0;
}