Given a pattern and a string str, find if str follows the same pattern.

Here follow means a full match, such that there is a bijection between a letter in pattern and a non-empty word in str.

Examples:

1. pattern = "abba", str = "dog cat cat dog" should return true.
2. pattern = "abba", str = "dog cat cat fish"
   should return false.
3. pattern = "aaaa", str = "dog cat cat dog" should return false.
4. pattern = "abba", str = "dog dog dog dog" should return false.

Notes:
You may assume pattern contains only lowercase letters, and str contains lowercase letters separated by a single space.

給定一個模式串pattern和一個字符串str，找到如果str是否遵循相同的模式。

使用了map、set、vector三種容器。利用map來存儲模式串字符與字符串中字符串的對應關系，利用set的性質來檢測pattern與str中的對應元素是否一一對應，利用vector存儲str中去除空格後的每一個單詞。

最後用map中模板的值構建新的字符串觀察是否與給定的str相等。

總的來說是一個分離+重構+比較的過程。

class Solution {
public:
    bool wordPattern(string pattern, string str) {
        istringstream istr(str);
        string s;
        vector
 
<string> svec;
        while (istr >> s)
            svec.push_back(s);
        if (pattern.size() != svec.size())
            return false;
        unordered_map<char, string> c2s;
        unordered_set<char> cs;
        unordered_set<string> ss(svec.begin(), svec.end());
        for (char c : pattern)
            cs.insert(c);
        if (cs.size() != ss.size())
            return false;
        for (int i = 0; i != pattern.size(); i++) {
            c2s[pattern[i]] = svec[i];
        }
        string tmp;
        for (auto c : pattern) {
            tmp += (c2s[c] + " ");
        }
        if (tmp != str + " ")
            return false;
        return true;
    }
};
// 0 ms

[LeetCode] Word Pattern