leetcode383. Ransom Note

Given an arbitrary ransom note string and another string containing letters from all the magazines, write a function that will return true if the ransom note can be constructed from the magazines ; otherwise, it will return false.

Each letter in the magazine string can only be used once in your ransom note.

Note:
You may assume that both strings contain only lowercase letters.

canConstruct("a", "b") -> false
canConstruct("aa", "ab") -> false
canConstruct("aa", "aab") -> true

    public boolean canConstruct(String ransomNote, String magazine) {
        if(ransomNote.isEmpty()) return true;
        if(ransomNote.length() > magazine.length()) return false;
        int p1 = 0, p2 = 0;
        int[] count = new int[26];
        int wordCount = 0;
        while(p1 < ransomNote.length() && p2 < ransomNote.length()) {
            char c1 = ransomNote.charAt(p1);
            char c2 = magazine.charAt(p2);
            if(++count[c1-'a'] == 1) {
                wordCount++;
            }
            if(--count[c2-'a'] == 0) {
                wordCount--;
            }
            
            p1++;
            p2++;
        }
        
        while(p2 < magazine.length()) {
            if(wordCount == 0) break;
            char c = magazine.charAt(p2);
            count[c-'a']--;
            if(count[c-'a'] == 0) {
                wordCount--;
            }
            p2++;
        }
        return wordCount == 0;
    }

    public boolean canConstruct(String ransomNote, String magazine) {
        int len=ransomNote.length();
        int[] index = new int[128];
        for(int i = 0; i < len; i++){
            char cu=ransomNote.charAt(i);
            int result=magazine.indexOf(cu,index[cu]);
            if(result == -1){
                return false;
            }
            else{
                index[cu]=result + 1;   
            }   
        }
        return true;
    }