leetcode-第10周双周赛-5081-歩进数

题目描述：

自己的提交：参考全排列

class Solution:
    def countSteppingNumbers(self, low: int, high: int) -> List[int]:
        a = [i for i in range(10)]
        res =[]
        def helper(num):
            if low<=num<=high and num not in res:
                res.append(num)
            if num>=high:
                return
            if num%10+1<=9:helper(num*10+(num%10+1))
            if num%10-1>=0:helper(num*10+(num%10-1))
        for i in a:
            helper(i)
        res.sort()
        return res

优化：

class Solution(object):
    def countSteppingNumbers(self, low, high):
        ans = set()
        def search(x):
            if x > high: return
            if x >= low: ans.add(x)
            last = x % 10
            for d in (last-1, last+1):
                if 0 <= d < 10:
                    search(10 * x + d)
        for d in range(10): search(d)
        return sorted(ans)