Question
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:
Swill have length in range[1, 500].Swill consist of lowercase letters ('a'to'z') only.
Solution
TODO
Code
Here is a sample solution.
class Solution {
public List<Integer> partitionLabels(String S) {
List<Integer> list = new ArrayList();
int[] ends = new int[26];
for(int i=0; i<S.length(); i++) {
ends[S.charAt(i) - 'a'] = i;
}
int start = 0;
int end = -1;
for(int i=0; i<S.length(); i++) {
if(ends[S.charAt(i) - 'a'] > end) {
end = ends[S.charAt(i) - 'a'];
}
if(i == end){
list.add(end-start + 1);
start = i+1;
}
}
return list;
}
}
Performance
O(n)