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.

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.

Note:

1. S will have length in range [1, 500].
2. S will consist of lowercase letters ('a' to 'z') only.

class Solution(object):
    def partitionLabels(self, S):
        """
        :type S: str
        :rtype: List[int]
        """
        
        #记录每个元素最后一次出现的位置
        d = {c:i for i,c in enumerate(S)}
        
        res = []
        start=end = 0
        
        for i,c in enumerate(S):
            #设置尾部
            end = max(end, d[c])
            #当区间里所有元素都遍历过，设置下一个头部
            if i == end:
                res.append(end-start+1)
                start = i+1
                
        return res