Substring with Concatenation of All Words

標籤：java   leetcode   字串   

題目

You are given a string, S, and a list of words, L, that are all of the same length. Find all starting indices of substring(s) in S that is a concatenation of each word in L exactly once and without any intervening characters.

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

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

方法

使用map來儲存，並進行判斷。

    public List<Integer> findSubstring(String S, String[] L) {        List<Integer> list = new ArrayList<Integer>();        int arrLen = L.length;        int strLen = L[0].length();        Map<String, Integer> map = new HashMap<String, Integer>();        for (int i = 0; i < arrLen; i++) {        if (map.get(L[i]) == null) {        map.put(L[i], 1);        } else {        map.put(L[i], map.get(L[i]) + 1);        }        }                Map<String, Integer> tempMap = new HashMap<String, Integer>();        for (int i = 0; i < S.length() - arrLen * strLen + 1; i++) {        tempMap.clear();        boolean flag = true;        for (int j = 0; j < arrLen && flag; j++) {        String str = S.substring(i + j * strLen, i + (j + 1 )* strLen);        if (map.containsKey(str)) {        tempMap.put(str, tempMap.get(str) == null ? 1 : tempMap.get(str) + 1);            if (tempMap.get(str) > map.get(str)) {            flag = false;            }        } else {        flag = false;        }        }        if (flag) {        list.add(i);        }        }        return list;    }