LeetCode Online Judge 题目C# 练习 - Substring with Concatenation of All Words

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).

 1         public static List<int> SubstringwithConcatenationofAllWords(string S, List<string> L)

 2         {

 3             List<int> ret = new List<int>();

 4             Dictionary<string, int> map_count = new Dictionary<string, int>();

 5             Dictionary<string, int> map_found = new Dictionary<string, int>();

 6             int l = L[0].Length;

 7             int total = L.Count;

 8 

 9             //Add words in L to the map_count

10             for (int i = 0; i < total; i++)

11             {

12                 if (map_count.ContainsKey(L[i]))

13                     map_count[L[i]]++;

14                 else

15                     map_count.Add(L[i], 1);

16             }

17 

18             //last index need to check

19             int last = S.Length - l * total;

20             for (int i = 0; i <= last; i++)

21             {

22                 int index = i;

23                 string sub = S.Substring(index, l);

24                 for(int j = 0; j < total; j++)

25                 {

26                     if (!map_count.ContainsKey(sub))

27                         break;

28                     else if (map_found.ContainsKey(sub) && map_found[sub] >= map_count[sub])

29                         break;

30                     else

31                     {

32                         if (map_found.ContainsKey(sub))

33                             map_found[sub]++;

34                         else

35                             map_found.Add(sub, 1);

36                         index += l;

37                         sub = S.Substring(index, l);

38                     }

39 

40                     if (j == total - 1)

41                     {

42                         ret.Add(i);

43                     }

44                 }

45 

46                 map_found.Clear();

47             }

48 

49             return ret;

50         }

代码分析：

　　这个代码过不了大数据，Time Limit Exceeded。 可能是SubString这个方法比较耗性能。

　　这个是别人用JAVA做的，能过大数据，先往下复习，回头再看 http://heartfire.cc/wp/substring-with-concatenation-of-all-words/