Leetcode 467. 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.

Code (Java):

class Solution {
    public int findSubstringInWraproundString(String p) {
        if (p == null || p.length() == 0) {
            return 0;
        }
        
        int[] count = new int[26];
        int ans = 0;
        int maxLen = 1;
        count[p.charAt(0) - 'a'] = 1;
        
        for (int i = 1; i < p.length(); i++) {
            char curr = p.charAt(i);
            char prev = p.charAt(i - 1);
            
            if (Character.getNumericValue(curr) == Character.getNumericValue(prev) + 1 
                || (prev == 'z' && curr == 'a')) {
                maxLen++;
            } else {
                maxLen = 1;
            }
            
            count[curr - 'a'] = Math.max(count[curr - 'a'], maxLen);
        }
        
        for (int i = 0; i < count.length; i++) {
            ans += count[i];
        }
                
        return ans;
    }
}