reconstruct-original-digits-from-english.py

# Time:  O(n)
# Space: O(1)

# Given a non-empty string containing an out-of-order English representation
# of digits 0-9, output the digits in ascending order.
#
# Note:
# Input contains only lowercase English letters.
# Input is guaranteed to be valid and can be transformed to its original digits.
# That means invalid inputs such as "abc" or "zerone" are not permitted.
# Input length is less than 50,000.
# Example 1:
# Input: "owoztneoer"
#
# Output: "012"
# Example 2:
# Input: "fviefuro"
#
# Output: "45"

from collections import Counter

class Solution(object):
    def originalDigits(self, s):
        """
        :type s: str
        :rtype: str
        """
        # The count of each char in each number string.
        cnts = [Counter(_) for _ in ["zero", "one", "two", "three", \
                                     "four", "five", "six", "seven", \
                                     "eight", "nine"]]
        
        # The order for greedy method.
        order = [0, 2, 4, 6, 8, 1, 3, 5, 7, 9]
        
        # The unique char in the order.
        unique_chars = ['z', 'o', 'w', 't', 'u', \
                        'f', 'x', 's', 'g', 'n']

        cnt = Counter(list(s))
        res = []
        for i in order:
            while cnt[unique_chars[i]] > 0:
                cnt -= cnts[i]
                res.append(i)
        res.sort()

        return "".join(map(str, res))