Custom Sort String(math)

SandTare strings composed of lowercase letters. InS, no letter occurs more than once.

Swas sorted in some custom order previously. We want to permute the characters ofTso that they match the order thatSwas sorted. More specifically, ifxoccurs beforeyinS, thenxshould occur beforeyin the returned string.

Return any permutation ofT(as a string) that satisfies this property.

Example :
Input:

S = "cba"
T = "abcd"

Output:
 "cbad"

Explanation:

"a", "b", "c" appear in S, so the order of "a", "b", "c" should be "c", "b", and "a". 
Since "d" does not appear in S, it can be at any position in T. "dcba", "cdba", "cbda" are also valid outputs.

Note:

S has length at most 26, and no character is repeated in S.
T has length at most 200.
S and T consist of lowercase letters only.

分析

算出来T里每个char的count

先遍历S输出所有 [i*count[i]] 然后把T剩下的输出，还是[i*count[i]]

import collections


class Solution:
    def customSortString(self, S, T):
        """
        :type S: str
        :type T: str
        :rtype: str
        """
        count = collections.defaultdict(int)
        l = []
        for i in T:
            count[i] += 1

        for i in S:
            if i in count:
                l+=[i * count[i]]
                count[i] = 0
        l+=[i*count[i] for i in count]
        return ''.join(l)