[leetcode-290-Word Pattern]-优快云博客

本文介绍了一种基于双映射的方法来判断字符串是否符合给定的模式。通过使用两个哈希表跟踪模式到字符串及字符串到模式的对应关系，确保模式与字符串间存在一对一的全匹配关系。

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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.

思路：

用两个map分别存储pattern对应的单词，以及单词对应的pattern。

bool wordPattern(string pattern, string str)
{
    stringstream ss(str);
    map<string, char>s2ch;
    map<char, string>ch2s;
    vector<string>s;
    string temp;
    while (ss >> temp) s.push_back(temp);     
    if (s.size() != pattern.length())return false;

    for (int i = 0; i < s.size();i++)
    {
        if (s2ch[s[i]] == 0 && ch2s[pattern[i]] == "")
        {
            s2ch[s[i]] = pattern[i];
            ch2s[pattern[i]] = s[i];
            continue;
        }
        if (s2ch[s[i]] != pattern[i]) return false;
    }
    return true;
}