[LeetCode] #30 Substring with Concatenation of All Words

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) in s that is a concatenation of each word in wordsexactly once and without any intervening characters.

For example, given:
s: "barfoothefoobarman"
words: ["foo", "bar"]

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

本题是寻找字符串中子串集出现的位置，先对子串集做成字典，然后依次匹配。时间：568ms，代码如下：

class Solution {
public:
    vector<int> findSubstring(string s, vector<string>& words) {
        vector<int> res;
        if (s.empty() || words.empty() || s.size() < words.size()*words[0].size())
            return res;
        int  searchEnd = s.size() - words.size() * words[0].size();
        size_t wordLen = words[0].size(), wordNum = words.size();
        map<string, int> total, submap;
        for (size_t i = 0; i < wordNum; ++i)
            total[words[i]]++;
        for (size_t i = 0; i <= searchEnd; ++i){
            submap.clear();
            size_t k = 0;
            for (size_t j = i; k < wordNum; j += wordLen, ++k){
                string str = s.substr(j, wordLen);
                if (total.find(str) == total.end())
                    break;
                else if (++submap[str]>total[str])
                    break;
            }
            if (k == words.size())
                res.push_back(i);
        }
        return res;
    }
};