[Leetcode] 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].

老是超时，终于过了。

 1 class Solution {

 2 public:

 3     vector<int> findSubstring(string S, vector<string> &L) {

 4         vector<int> res;

 5         if (L.size() < 1) return res;

 6         

 7         int Len = L.size() * L[0].length();

 8         int len = L[0].length();

 9         if (S.length() < Len) return res;

10         

11         map<string, int> word_count;

12         for (int i = 0; i < L.size(); ++i) {

13             word_count[L[i]]++;

14         }

15         map<string, int> word_detect;

16         for (int i = 0; i <= S.length() - Len; ++i) {

17             word_detect.clear();

18             string substr;

19             int j = 0;

20             for (j = 0; j < Len; j += len) {

21                 substr = S.substr(i + j, len);

22                 if (word_count.find(substr) == word_count.end())

23                     break;

24                 ++word_detect[substr];

25                 if (word_detect[substr] > word_count[substr])

26                     break;

27             }

28             if (j==Len) res.push_back(i);

29         }

30         return res;

31     }

32 };