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.

Example 1:

Input: pattern = "abba", str = "dog cat cat dog"
Output: true

Example 2:

Input:pattern = "abba", str = "dog cat cat fish"
Output: false

Example 3:

Input: pattern = "aaaa", str = "dog cat cat dog"
Output: false

Example 4:

Input: pattern = "abba", str = "dog dog dog dog"
Output: false

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

Runtime: 0 ms, faster than 100.00% of C++ online submissions for Word Pattern.

class Solution {
public:
    bool wordPattern(string pattern, string str) {
        map<char, int> patternMap;
        map<string, int> wordMap;
        istringstream in(str);
        int i = 0, n = pattern.size();
        for (string word; in >> word; i++)
        {
            if (i == n || patternMap[pattern[i]] != wordMap[word])
            {
                return false;
            }
            patternMap[pattern[i]] = wordMap[word] = i + 1;
        }
        return i == n;
    }
};