[leetcode-290-Word Pattern]

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.

思路：

用两个map分别存储pattern对应的单词，以及单词对应的pattern。

bool wordPattern(string pattern, string str)
{
    stringstream ss(str);
    map<string, char>s2ch;
    map<char, string>ch2s;
    vector<string>s;
    string temp;
    while (ss >> temp) s.push_back(temp);     
    if (s.size() != pattern.length())return false;

    for (int i = 0; i < s.size();i++)
    {
        if (s2ch[s[i]] == 0 && ch2s[pattern[i]] == "")
        {
            s2ch[s[i]] = pattern[i];
            ch2s[pattern[i]] = s[i];
            continue;
        }
        if (s2ch[s[i]] != pattern[i]) return false;
    }
    return true;
}

参考：

https://discuss.leetcode.com/topic/26313/0ms-c-solution-using-istringstream-and-double-maps