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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.
strobogramatic数字是旋转180度时看起来相同的数字（上下颠倒）。
编写一个函数来计算在low<=num<=high范围内存在的总strobogrammatic数。
例子：
输入：low=“50”，high=“100”
输出：3
说明：69、88和96是三个strobogramatic数字。
注：
因为范围可能是一个大数字，所以低数字和高数字表示为字符串。
1 class Solution { 2 func strobogrammaticInRange(_ low:String,_ high:String) -> Int { 3 var res:Int = 0 4 find(low, high, "", &res) 5 find(low, high, "0", &res) 6 find(low, high, "1", &res) 7 find(low, high, "8", &res) 8 return res; 9 } 10 11 func find (_ low:String,_ high:String,_ w:String,_ res:inout Int) 12 { 13 if w.count >= low.count && w.count <= high.count 14 { 15 if (w.count == low.count && w < low) || (w.count == high.count && w > high) 16 { 17 return 18 } 19 if !(w.count > 1 && w[0] == "0") 20 { 21 res += 1 22 } 23 } 24 if w.count + 2 > high.count 25 { 26 return 27 } 28 find(low, high, "0" + w + "0", &res) 29 find(low, high, "1" + w + "1", &res) 30 find(low, high, "6" + w + "9", &res) 31 find(low, high, "8" + w + "8", &res) 32 find(low, high, "9" + w + "6", &res) 33 } 34 } 35 36 extension String { 37 //subscript函数可以检索数组中的值 38 //直接按照索引方式截取指定索引的字符 39 subscript (_ i: Int) -> Character { 40 //读取字符 41 get {return self[index(startIndex, offsetBy: i)]} 42 } 43 }