LeetCode-in-All

763. Partition Labels

Medium

You are given a string s. We want to partition the string into as many parts as possible so that each letter appears in at most one part.

Return a list of integers representing the size of these parts.

Example 1:

Input: s = “ababcbacadefegdehijhklij”

Output: [9,7,8]

Explanation:

The partition is "ababcbaca", "defegde", "hijhklij".
This is a partition so that each letter appears in at most one part.
A partition like "ababcbacadefegde", "hijhklij" is incorrect, because it splits s into less parts. 

Example 2:

Input: s = “eccbbbbdec”

Output: [10]

Constraints:

• 1 <= s.length <= 500
• s consists of lowercase English letters.

Solution

class Solution:
    def partitionLabels(self, s: str) -> List[int]:
        letters = list(s)
        result = []
        position = [0] * 26

        for i in range(len(letters)):
            position[ord(letters[i]) - ord('a')] = i

        i = 0
        prev = -1
        max_pos = 0

        while i < len(letters):
            if position[ord(letters[i]) - ord('a')] > max_pos:
                max_pos = position[ord(letters[i]) - ord('a')]
            if i == max_pos:
                result.append(i - prev)
                prev = i
            i += 1

        return result

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