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.

Solution 1: Greedy

class Solution {
    public List<Integer> partitionLabels(String S) {
        int last[] = new int[26];
        for (int i = 0; i < S.length(); i++) {
            last[S.charAt(i) - 'a'] = i;
        }
        List<Integer> ans = new ArrayList<>();
        int j = 0, anchor = 0;
        for (int i = 0; i < S.length(); i++) {
            j = Math.max(j, last[S.charAt(i) - 'a']);
            if (i == j) {
                ans.add(j - anchor + 1);
                anchor = j + 1;
            }
        }
        return ans;
    }
}

Categories: Algorithm