题目：

题解：

def canCross(stones: List[int]) -> bool:
    @lru_cache(None)
    def dfs(pos,step):
        if pos==stones[-1]: return True
        for d in [-1,0,1]:
            if step+d>0 and pos+step+d in set(stones):
                if dfs(pos+step+d, step+d):
                    return True
        return False
    pos, step = 0, 0
    return dfs(pos, step)