TYVJ P2032 「Poetize9」升降梯上 spfa最短路

#include<cstdio>
#include<iostream>
#include<queue>
#include<cstring>
#include<cmath>
#define R register int
using namespace std;
inline int g() {
    R ret=0,fix=1; register char ch; while(!isdigit(ch=getchar())) fix=ch==‘-‘?-1:fix;
    do ret=ret*10+(ch^48); while(isdigit(ch=getchar())); return ret*fix;
}
struct node{
    int u,pos;
    node() {}
    node(int uu,int ppos):u(uu),pos(ppos) {}
}e[1010];
queue<node>q;
bool vis[1010][24];
int n,m,z,ans=0x3f3f3f3f,d[1010][24],a[24];
inline void spafa() {
    memset(d,0x3f,sizeof(d));
    q.push(node(1,z)); vis[1][z]=true,d[1][z]=0;
    while(q.size()) {
        R u=q.front().u,pos=q.front().pos; q.pop(); vis[u][pos]=false;
        for(R i=1;i<=m;++i) {
            if(u+a[i]<=0) continue; if(u+a[i]>n) break;
            if(d[u+a[i]][i]>d[u][pos]+abs(i-pos)+abs(a[i])*2) {
                d[u+a[i]][i]=d[u][pos]+abs(i-pos)+abs(a[i])*2;
                if(vis[u+a[i]][i]) continue;
                vis[u+a[i]][i]=true; q.push(node(u+a[i],i));
            }
        }
    }
}
signed main() {
    freopen("up.in","r",stdin);
    freopen("up.out","w",stdout);
    n=g(),m=g(); 
    for(R i=1;i<=m;++i) {a[i]=g(); if(!a[i]) z=i;}
    spafa(); for(R i=1;i<=m;++i) ans=min(ans,d[n][i]);
    if(ans==0x3f3f3f3f) printf("-1\n");
    else printf("%d",ans);
}