290. Word Pattern

290. Word Pattern (Easy)

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 that may be separated by a single space.

Related Topics:
Hash Table

Similar Questions:

• Isomorphic Strings (Easy)
• Word Pattern II (Hard)

Solution 1.

// OJ: https://leetcode.com/problems/word-pattern/
// Author: github.com/lzl124631x
// Time: O(M + N)
// Space: O(M + N)
class Solution {
public:
    bool wordPattern(string pattern, string str) {
        unordered_map<char, string> m;
        unordered_map<string, char> r;
        istringstream ss(str);
        string word;
        for (char c : pattern) {
            if (!(ss >> word)) return false;
            if ((m.count(c) && m[c] != word)
                || r.count(word) && r[word] != c) return false;
            m[c] = word;
            r[word] = c;
        }
        return ss.eof();
    }
};