791. Custom Sort String.py

class Solution:
    def customSortString(self, order: str, s: str) -> str:
        result = ""
        mp = {}
        for char in s:
            mp[char] = mp.get(char, 0) + 1
        for char in order:
            if char in mp:
                result += char * mp[char]
                del mp[char]
        for char, count in mp.items():
            result += char * count
        return result