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：使用两个map记录是否pattern和str匹配。

注意，map的键值这里不能为0，因为为0时map默认是访问了未创建过的键，因此要从1开始。

此外，for循环里真的可以实现很多东西，用好了会让代码很精简。

class Solution {
public:
    bool wordPattern(string pattern, string str) {
        map<char, int> dict1;
        map<string, int> dict2;
        stringstream ss(str);
        int i = 0, n = pattern.size();
        for (string word; ss >> word; i++)
        {
            if (i == n || dict1[pattern[i]] != dict2[word])
                return false;
            dict1[pattern[i]] = dict2[word] = i + 1;
        }
        return i == n;
    }
};