# 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.

**The Idea:** Use a bidirectional map to check for a one to one mapping between each character in the pattern and each word in the sentence.

**Complexity:** O(n) time and O(2n) space:

```python
def wordPattern(self, pattern, str):
    """
    :type pattern: str
    :type str: str
    :rtype: bool
    """
    if len(pattern) != len(str.split()):
        return False
    chars_word = {}
    word_char = {}
    for char, word in zip(pattern, str.split()):
        if (chars_word.__contains__(char) and chars_word[char] != word)\
                or word_char.__contains__(word) and word_char[word] != char:
            return False
        elif not chars_word.__contains__(char):
            chars_word[char] = word
            word_char[word] = char

    return True
```