Codeforces 500A - New Year Transportation【DFS】

 1 #include<iostream>  
 2 #include<cstdio>  
 3 #include<cstring> 
 4 #include <cmath> 
 5 #include<stack>
 6 #include<vector>
 7 #include<map> 
 8 #include<set>
 9 #include<queue> 
10 #include<algorithm>  
11 #define mod=1e9+7;
12 using namespace std;
13 
14 typedef long long LL;
15 const int INF = 0x7fffffff;
16 const int maxn=50005;
17 int a[maxn],vis[maxn];
18 int n,t;
19 int flag=0;
20 
21 void dfs(int x){
22     if(vis[x]) return;
23     vis[x]=1;
24     int xx=x+a[x];
25     if(xx==t){
26         flag=1;
27         return;
28     }
29     dfs(xx);
30 }
31 
32 int main(){
33     scanf("%d %d",&n,&t);
34     memset(vis,0,sizeof(vis));
35     for(int i=1;i<n;i++) scanf("%d",&a[i]);
36     dfs(1);
37     if(flag) printf("YES\n");
38     else printf("NO\n");
39     return 0;
40 }