【leetcode】1215.Stepping Numbers

题目如下：

A Stepping Number is an integer such that all of its adjacent digits have an absolute difference of exactly 1. For example, 321 is a Stepping Number while 421 is not.

Given two integers low and high, find and return a sorted list of all the Stepping Numbers in the range [low, high] inclusive.

Example 1:
Input: low = 0, high = 21

Output: [0,1,2,3,4,5,6,7,8,9,10,12,21]
Constraints:

0 <= low <= high <= 2 * 10^9

解题思路：如果x是一个Stepping Number，假设x的个位是y，那么x*10 + y - 1 (y-1 >=0) 和 x*10 + y + 1 (y+1<=9) 也是Stepping Number，根据这个规律把所有符合条件的数字求出来即可。

代码如下：

class Solution(object):

    def countSteppingNumbers(self, low, high):

        """

        :type low: int

        :type high: int

        :rtype: List[int]

        """

        queue = range(0,10)

        res = set()

        while len(queue) > 0:

            val = queue.pop(0)

            if val >= low and val <= high:

                res.add(val)

            last = int(str(val)[-1])

            if last < 9:

                new_val = int(str(val) + str(last+1))

                if new_val <= high:

                    queue.append(new_val)

            if last > 0:

                new_val = int(str(val) + str(last-1))

                if new_val <= high:

                    queue.append(new_val)

        return sorted(list(res))

巴特西

【leetcode】1215.Stepping Numbers

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