# Question

Formatted question description: https://leetcode.ca/all/248.html

 248	Strobogrammatic Number III

A strobogrammatic number is a number that looks the same when rotated 180 degrees (looked at upside down).

Write a function to count the total strobogrammatic numbers that exist in the range of low <= num <= high.

Example:

Input: low = "50", high = "100"
Output: 3
Explanation: 69, 88, and 96 are three strobogrammatic numbers.

Note:
Because the range might be a large number, the lowand high numbers are represented as string.



# Algorithm

Goal is to get the number of symmetry numbers in a given range.

Initialize the cases of n=0 and n=1, and then recurse based on them.

The recursion length len is traversed from low to high, and then see if the current word length reaches len,

• If it is reached, first remove the multiple digits that start with 0,
• Then remove the numbers with the same length as low but less than low, and numbers with the same length as high but greater than high,
• Then the result is incremented by 1,
• Then add the five pairs of symmetric numbers to the left and right of the current word, and continue to call recursively

Java