题解

#include<iostream>
#include<queue>
using namespace std;
int n,x,y,arr[210],vis[210];
struct node{
    int x;
    int step;
};
queue<node> q;
int main(){
    cin>>n>>x>>y;
    for(int i=1;i<=n;i++) cin>>arr[i];
    q.push({x,0});
    while(!q.empty()){
        node t=q.front();
        q.pop();
        vis[t.x]=1;
        if(t.x==y){cout<<t.step;return 0;}
        int nx=t.x+arr[t.x];
        if(nx>=1&&nx<=n&&vis[nx]==0){q.push({nx,t.step+1});}
        nx=t.x-arr[t.x];
        if(nx>=1&&nx<=n&&vis[nx]==0){q.push({nx,t.step+1});}
    }
    cout<<-1;
    return 0;
}