Increasing Decreasing String — LeetCode 1370 Python Solution

The problem

You are given a string s. Reorder the string using the following algorithm: Remove the smallest character from s and append it to the result.

Example

Input

s = "aaaabbbbcccc"

Output

"abccbaabccba"

Explanation

After steps 1, 2 and 3 of the first iteration, result = "abc"

Python solution

class Solution:
    def sortString(self, s: str) -> str:
        cnt = Counter(s)
        cs = ascii_lowercase + ascii_lowercase[::-1]
        ans = []
        while len(ans) < len(s):
            for c in cs:
                if cnt[c]:
                    ans.append(c)
                    cnt[c] -= 1
        return "".join(ans)

Complexity

Pattern: Hash Map

Trade memory for time: remember what you have seen so the second pass never happens. LeetCode 1370. Increasing Decreasing String is filed here on both counts: the reference solution below belongs to the algorithm family this hub collects, and LeetCode tags it Hash Table and Counting.

The hash map guide has the Python template for the pattern and the 709 LeetCode problems that use it.

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