该系列共三道题，Company Tag只有一个Google，那就必须要做了。

第一题题目内容

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

Write a function to determine if a number is strobogrammatic. The number is represented as a string.

For example, the numbers "69", "88", and "818" are all strobogrammatic.

解决思路

直接按照题目要求来，人家要什么就给什么，这题要求判断，那就判断。从两头开始，我这边是1，那翻过来还是1，0和8都是，有区别的就是6和9，因为上下颠倒很有可能导致性别的不同，所以左边是6的话，对称位置必须是9。所以这题先建立一个对应的map，然后扫一遍字符串就可以了。

code

复杂度分析

第二题题目内容

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

Find all strobogrammatic numbers that are of length = n.

For example,
Given n = 2, return ["11","69","88","96"].

解决思路

一看关键词find/return all #$%^，通常都是DFS，深搜一遍，挖地三尺，雁过拔毛。

code

复杂度分析

第三题题目内容

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.

For example,
Given low = "50", high = "100", return 3. Because 69, 88, and 96 are three strobogrammatic numbers.

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

解决思路

code

复杂度分析