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hashtable+双指针窗口法解题思路

最近一直在刷leetcode，发现许多题目解法很相似，如求 findSubstring，minWindow，lengthOfLongestSubstring问题，解法大致都一样都是用滑动窗口的思想，不过滑动的规则没处理好，很容易导致时间复杂度增加；

题目链接：

https://leetcode.com/problems/substring-with-concatenation-of-all-words/

；


http://oj.leetcode.com/problems/minimum-window-substring/

；


http://oj.leetcode.com/problems/longest-substring-without-repeating-characters/

；

//链接1题解
public ArrayList<Integer> findSubstring(String S, String[] L) {
    // Note: The Solution object is instantiated only once and is reused by each test case.
    ArrayList<Integer> res = new ArrayList<Integer>();
    if(S==null || S.length()==0 || L==null || L.length==0)
        return res;
    HashMap<String,Integer> map = new HashMap<String,Integer>();
    for(int i=0;i<L.length;i++)
    {
        if(map.containsKey(L[i]))
        {
            map.put(L[i],map.get(L[i])+1);
        }
        else
        {
            map.put(L[i],1);
        }
    }
    for(int i=0;i<L[0].