#37267: Python不能過:(
s11104220@school.saihs.edu.tw
(施同學)
School
:
臺北市立松山高級工農職業學校
ID : 221254
IP address : [118.165.10.104]
Last Login ：
2023-10-21 21:29:09
def main():
from sys import stdin
from collections import deque
n,P,L,R=map(int,stdin.readline().split())
tel=tuple(map(int,stdin.readline().split()))
t=deque([[0,0]])
vis=set()
while t:
x,d=t.popleft()
if x==P:print(d);break
for i in (-L,R):
nx=x+i
if nx>=0 and nx<n:
if nx not in vis:
vis.add(nx)
nnx=tel[nx]
if nnx>=0 and nnx<n:
t.append([nnx,d+1])
else:print(-1)
if __name__=="__main__":main()
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