leetcode467. Unique Substrings in Wraparound String

Consider the string s to be the infinite wraparound string of "abcdefghijklmnopqrstuvwxyz", so s will look like this: "...zabcdefghijklmnopqrstuvwxyzabcdefghijklmnopqrstuvwxyzabcd....".

Now we have another string p. Your job is to find out how many unique non-empty substrings of p are present in s. In particular, your input is the string p and you need to output the number of different non-empty substrings of p in the string s.

Note: p consists of only lowercase English letters and the size of p might be over 10000.

Example 1:
Input: "a"
Output: 1

Explanation: Only the substring "a" of string "a" is in the string s.
Example 2:
Input: "cac"
Output: 2
Explanation: There are two substrings "a", "c" of string "cac" in the string s.
Example 3:
Input: "zab"
Output: 6
Explanation: There are six substrings "z", "a", "b", "za", "ab", "zab" of string "zab" in the string s.

    public int findSubstringInWraproundString(String p) {
        int[] preMaxSubstring = new int[26];
        int prevLength = 0;
        int count = 0;
        for(int i = 0 ; i<p.length() ; i++) {
            char c = p.charAt(i);
            if(i == 0) {
                count++;
                preMaxSubstring[c-'a']++;
                prevLength++;
            }else {
                char prev = p.charAt(i-1);
                prevLength = (prev-'a'+1) % 26 == (c-'a') ? prevLength+1 : 1;
                if(prevLength > preMaxSubstring[c-'a']) {
                    count += prevLength - preMaxSubstring[c-'a'];
                    preMaxSubstring[c-'a'] = prevLength;
                }
            }
        }
        return count;
    }