763. Partition Labels

A string S of lowercase English 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:

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

class Solution {
    public List<Integer> partitionLabels(String S) {
            if(S == null || S.length() == 0){
                return null;
            }
            List<Integer> list = new ArrayList<>();
            int[] map = new int[26];  // record the last index of the each char

            for(int i = 0; i < S.length(); i++){
                map[S.charAt(i)-'a'] = i;
            }
            // record the end index of the current sub string
            int last = 0;
            int start = 0;
            for(int i = 0; i < S.length(); i++){
                last = Math.max(last, map[S.charAt(i)-'a']);
                if(last == i){
                    list.add(last - start + 1);
                    start = last + 1;
                }
            }
            return list;
        }
}

叹气，明明这么简单