290. Word Pattern（LeetCode）

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.

class Solution {
public:
    bool wordPattern(string pattern, string str) {
       istringstream strcin(str);
        string s;
        vector<string> vs;
        while(strcin >> s) vs.push_back(s);
        if (pattern.size() != vs.size()) return false;
        map<string, char> s2c;
        map<char, string> c2s;
        for (int i = 0; i < vs.size(); ++i) {
            if (s2c[vs[i]] == 0 && c2s[pattern[i]] == "") { 
                s2c[vs[i]] = pattern[i]; 
                c2s[pattern[i]] = vs[i]; 
                continue; 
            }
            if (s2c[vs[i]] != pattern[i]) return false;
        }
        return true;
    }
};