# 763. Partition Labels

A string S of lowercase letters is given. We want to partition this string into as many parts as possible so that each letter appears in at most one part, and return a list of integers representing the size of these parts.


Input: S = "ababcbacadefegdehijhklij"
Output: [9,7,8]
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.

# Solution

Approach 1: build an index of first and last occurence of all characters.

# Code (Python)

Approach 1:

    def partitionLabels(self, S: str) -> List[int]:
        # idea: like merge intervals, but first need to build a map of "intervals" for each letter
        intervals = {}
        for i, letter in enumerate(S):
            if letter not in intervals:
                intervals[letter] = [i, i]
                intervals[letter][-1] = i
        chunks = []
        for interval in sorted(intervals.values()):
            if not chunks or interval[0] > chunks[-1][1]:
                chunks[-1][1] = max(chunks[-1][1], interval[1])
        return [chunk[1] - chunk[0] + 1 for chunk in chunks]

# Code (C++)

Approach 1:

Approach 2: