洛谷B3626评测失败，求指导

Question

洛谷B3626。这是我写的源代码

// Problem: B3626 跳跃机器人
// Contest: Luogu
// URL: https://www.luogu.com.cn/problem/B3626
// Memory Limit: 128 MB
// Time Limit: 1000 ms
// 
// Powered by CP Editor (https://cpeditor.org)

#include<bits/stdc++.h>
using namespace std;
bool bl(long long a,long long b,long long c)
{
    if((c-a)<=(b-c)) return true;
    else return false;
}
int main()
{
    long long n;
    cin>>n;
    long long sum;
    for(sum=0;n!=1;sum++)
    {
        long long p=ceil(sqrt(n*1.0)-1),q=floor(sqrt(n*1.0)+1);
        // cout<<p<<" "<<q<<endl;
        long long pp=p*p,qq=q*q;
        // cout<<pp<<" "<<qq<<endl;
        if(!(n%2)) n/=2;
        else if(sum==0) n--;
        else if(n==3) n--;
        else if(bl(pp,qq,n)) n--;
        else n++;
        // cout<<n<<endl<<endl;
    }
    cout<<sum<<endl;
    return 0;

}

但为什么只得了20分？

Answer 1

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

signed main()
{
    int n;
    cin>>n;
    vector<int>vis(n+1,-1);
    queue<int>s;
    s.push(1);
    vis[1]=0;
    while(!s.empty())
    {
        int cur=s.front();
        if(cur==n){cout<<vis[cur];return 0;}
        s.pop();
        int des[]={cur-1,cur+1,cur*2};
        for(int i=0;i<3;i++)
        {
            if(vis[des[i]]==-1&&des[i]>1&&des[i]<=n)
            {
                vis[des[i]]=vis[cur]+1;
                s.push(des[i]);
            }
        }
    }
    return 0;
}