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 shows the biggest last inde for our current substring
// now if we get i==last that means all the chars in this substring have all
// repetitions between start and last
last = Math.max(last, map[S.charAt(i) - 'a']);
if (last == i) {
list.add(last - start + 1);
start = last + 1;
}
}
return list;
}
}