Problem URL: Custom sort string

We will use a hashmap to store the order of characters in order. We will iterate over s and store the characters in a list. We will sort the list using the order of characters in order. We will return the res.

class Solution:
    def customSortString(self, order: str, s: str) -> str:
        res = ''
        count = collections.Counter(s)

        for ch in order:
            res += ch * count[ch]
            del count[ch]

        res += ''.join(cnt*count[cnt] for cnt in count)
        return res

Time complexity: O(n)
Space complexity: O(n)