代码如下

#include<queue>
#include<cstdio>
#include<iostream>
using namespace std;
typedef struct{
	int now;
	int step;
}floor;
int to[205]; 
queue<floor> que;
int flag[205]; 
int n,start,_end;
void BFS(int sf,int ef){ 
	floor flr;
	flr.now = sf;
	flr.step = 0;
	que.push(flr);
	flag[sf] = 1;
	while (!que.empty()){
		flr = que.front();
		que.pop();
		if(flr.now == ef) break;
		int h = flr.now +to[flr.now];
		if(h<=n && flag[h] == 0){
			flr.now = h;
			flr.step = flr.step+1;
			que.push(flr);
			flag[flr.now] = 1;
		}
		h= flr.now - to[flr.now];
		if(h>0 && flag[h] == 0){
			flr.now = h;
			flr.step = flr.step+1;
			que.push(flr);
			flag[flr.now] = 1;
		}
	}
	if(flr.now == ef) cout<<flr.step;
	else cout<<"-1";
}
int main(){
	cin>>n>>start>>_end;
	for (int i=1;i<=n;i++)
		cin>>to[i];
	BFS(start,_end);
	return 0;
}