1370. Increasing Decreasing String
https://leetcode.com/problems/increasing-decreasing-string
Description
Given a string s
. You should re-order the string using the following algorithm:
Pick the smallest character from
s
and append it to the result.Pick the smallest character from
s
which is greater than the last appended character to the result and append it.Repeat step 2 until you cannot pick more characters.
Pick the largest character from
s
and append it to the result.Pick the largest character from
s
which is smaller than the last appended character to the result and append it.Repeat step 5 until you cannot pick more characters.
Repeat the steps from 1 to 6 until you pick all characters from
s
.
In each step, If the smallest or the largest character appears more than once you can choose any occurrence and append it to the result.
Return the result string after sorting s
with this algorithm.
Example 1:
**Input:** s = "aaaabbbbcccc"
**Output:** "abccbaabccba"
**Explanation:** After steps 1, 2 and 3 of the first iteration, result = "abc"
After steps 4, 5 and 6 of the first iteration, result = "abccba"
First iteration is done. Now s = "aabbcc" and we go back to step 1
After steps 1, 2 and 3 of the second iteration, result = "abccbaabc"
After steps 4, 5 and 6 of the second iteration, result = "abccbaabccba"
Example 2:
**Input:** s = "rat"
**Output:** "art"
**Explanation:** The word "rat" becomes "art" after re-ordering it with the mentioned algorithm.
Example 3:
**Input:** s = "leetcode"
**Output:** "cdelotee"
Example 4:
**Input:** s = "ggggggg"
**Output:** "ggggggg"
Example 5:
**Input:** s = "spo"
**Output:** "ops"
Constraints:
1 <= s.length <= 500
s
contains only lower-case English letters.
ac
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