LeetCode290——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: pattern = "abba", str = "dog cat cat dog" should return true. pattern = "abba", str = "dog cat cat fish" should return false. pattern = "aaaa", str = "dog cat cat dog" should return false. 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.

实现：

class Solution {
public:
    int getNextWord(string& out, const string& str, int begin)
    {
        while (str[begin] == ' ')
        {
            begin++;
            if (begin >= str.length()) {
                return begin;
            }
        }
        int idx = begin;
        while (str[begin] != ' ' && str.length() > begin) {
            begin++;
        }
        out = str.substr(idx, begin - idx);
        return begin;
    }

    bool wordPattern(string pattern, string str) {
        int start = 0;
        string word;
        map smap;
        map cmap;
        for (int i = 0; i < pattern.size(); ++i)
        {
            if (start >= str.length()) return false;
            start = getNextWord(word, str, start);
            auto pos = smap.find(pattern[i]);
            auto iter = cmap.find(word);
            if (pos != smap.end()) {
                if (pos->second.compare(word) != 0)
                    return false;
            }
            else if (iter != cmap.end()){
                return false;
            }else{
                smap[pattern[i]] = word;
                cmap[word] = pattern[i];
            }
        }
        return start == str.length();
    }
};