LeetCode, leetcodeoj

LeetCode, leetcodeoj

Question:

You are given a string,S, And a list of words,Words, That are all of the same length. Find all starting indices of substring (s) inSThat is a concatenation of each word inWordsExactly once and without any intervening characters.

For example, given:
S:"barfoothefoobarman"
Words:["foo", "bar"]

You shoshould return the indices:[0,9].
(Order does not matter ).

Ideas:

Maintain a HashMap for words

package string;import java.util.ArrayList;import java.util.HashMap;import java.util.List;public class SubstringWithConcatenationOfAllWords {    public List<Integer> findSubstring(String s, String[] words) {        List<Integer> res = new ArrayList<Integer>();        int len;        int numWords;        int wordLen;        if (s == null || (numWords = words.length) == 0 || (len = s.length()) == 0) return res;        if (words == null || (wordLen = words[0].length()) == 0) return res;        int totalWordsLen = wordLen*numWords;        if (totalWordsLen > len) return res;        HashMap<String, Integer> map = new HashMap<String, Integer>();        for (String w : words) {            if (map.containsKey(w)) {                map.put(w, map.get(w) + 1);            } else {                map.put(w, 1);            }        }                for (int i = 0; i <= len - totalWordsLen; ++i) {            if (isSubString(s.substring(i, i + totalWordsLen), new HashMap<String, Integer>(map), wordLen)) {                res.add(i);            }        }                return res;    }        private boolean isSubString(String subStr, HashMap<String, Integer> map, int wordLen) {        for (int i = 0; i <= subStr.length() - wordLen; i += wordLen) {            String word = subStr.substring(i, i + wordLen);                        if (map.containsKey(word) && map.get(word) > 0) {                map.put(word, map.get(word) - 1);            } else {                return false; // If !contains or value is 0, return immediately.            }        }                for (String word : map.keySet()) {            if (map.get(word) != 0)                return false;        }                return true;    }        public static void main(String[] args) {        // TODO Auto-generated method stub        SubstringWithConcatenationOfAllWords s = new SubstringWithConcatenationOfAllWords();        String str = "barfoothefoobarman";        String[] words = {"foo", "bar"};        for(int i : s.findSubstring(str, words)) {            System.out.println(i);        }    }}