Strobogrammatic Number 系列 LC解題記錄（未完成）

該系列共三道題，Company Tag只有一個Google，那就必需要作了。

第一題題目內容

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.

解決思路

直接按照題目要求來，人家要什麼就給什麼，這題要求判斷，那就判斷。從兩頭開始，我這邊是1，那翻過來仍是1，0和8都是，有區別的就是6和9，由於上下顛倒頗有可能致使性別的不一樣，因此左邊是6的話，對稱位置必須是9。因此這題先創建一個對應的map，而後掃一遍字符串就能夠了。

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複雜度分析

第二題題目內容

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"].

解決思路

一看關鍵詞find/return all #$%^，一般都是DFS，深搜一遍，挖地三尺，雁過拔毛。

code

複雜度分析

第三題題目內容

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.

解決思路

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複雜度分析