先看看題目：
1309. Decrypt String from Alphabet to Integer Mapping
Easy
23123Add to ListShareGiven a string s formed by digits ('0' - '9') and '#' . We want to map s to English lowercase characters as follows:
- Characters (
'a'to'i')are represented by ('1'to'9') respectively. - Characters (
'j'to'z')are represented by ('10#'to'26#') respectively.
Return the string formed after mapping.
It's guaranteed that a unique mapping will always exist.
Example 1:
Input: s = "10#11#12" Output: "jkab" Explanation: "j" -> "10#" , "k" -> "11#" , "a" -> "1" , "b" -> "2".
Example 2:
Input: s = "1326#" Output: "acz"
Example 3:
Input: s = "25#" Output: "y"
Example 4:
Input: s = "12345678910#11#12#13#14#15#16#17#18#19#20#21#22#23#24#25#26#" Output: "abcdefghijklmnopqrstuvwxyz"
Constraints:
1 <= s.length <= 1000s[i]only contains digits letters ('0'-'9') and'#'letter.swill be valid string such that mapping is always possible.
附上通關證明：
我的想法：題目是說把數字1~9跟10#~26#轉換成英文字母，其實很簡單，就從尾巴開始，看到#就取出倒數二三個然後切割，沒有#就取一個然後切割，然後根據題目去做數字轉字母。
試著寫成js就過了，不過速度跟記憶算是慢的，我看了一下網路有自己造map的可能會比較快，但我懶，使用了預設函數。
/**
* @param {string} s
* @return {string}
*/
var freqAlphabets = function(s) {
result = ""
while(s.length>0){
lastchar = s.charAt(s.length-1)
alphabet="";
if(lastchar ==='#'){
alphabet = numToalphabet(s.substring(s.length-3,s.length-1))
s = s.substring(0,s.length-3)
}else{
alphabet = numToalphabet(s.substring(s.length-1,s.length))
s = s.substring(0,s.length-1)
}
result = alphabet + result
}
return result
}
function numToalphabet(numString){
return String.fromCharCode(parseInt(numString)+96)
}
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