LintCode 乱序字符串题目分析代码

public class Solution {
    /**
     * @param strs: A list of strings
     * @return: A list of strings
     */
  public ArrayList<String> anagrams(String[] strs) {
        HashMap<String,ArrayList<String>> hash = new HashMap<>();
        
        for(String str : strs) {
            // create unique label for each string
            String key = generalLabel(str);
            // map the label to a list of anagrams
            if(!hash.containsKey(key)) {
                ArrayList<String> temp = new ArrayList<>(); 
                hash.put(key, temp);
                temp.add(str);
            }
            else {
                hash.get(key).add(str);
            }
        }
        
        ArrayList<String> res = new ArrayList<>();
        
        for(ArrayList<String> anagram : hash.values()) {
             // ignore strings without anagrams
            if(anagram.size() > 1)
                res.addAll(anagram);
        }
        
        return res;
    }
    /*  
     * create a unique label for a string  
     * "cat", "atc" => a1c1t1  
     */  
    private String generalLabel(String str) {
        int[] hash = new int[26];
        for(int i=0;i<str.length();i++) {
            int idx = (int)(str.charAt(i)-'a');
            hash[idx]++;
        }
        
        StringBuilder sb = new StringBuilder();
        
        for(int i=0;i<26;i++) {
            if(hash[i] == 0)
                continue;
            char c = (char)('a' + i);
            sb.append(c);
            sb.append(hash[i]);
        }
        return sb.toString();
    }
}