leetcode:Word Pattern

最新推荐文章于 2024-11-28 09:45:26 发布

martin_liang

最新推荐文章于 2024-11-28 09:45:26 发布

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分类专栏：算法 leetcode C++/C

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本文介绍了一种用于判断给定字符串是否遵循指定模式的算法。该算法通过建立字符与单词之间的映射关系，确保模式与字符串内容完全匹配。文章详细解释了实现思路与代码逻辑，并通过几个示例验证了其正确性。

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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.

class Solution {
public:
    bool wordPattern(string pattern, string str) {

        vector<string> words;
        
        int leftIdx  = 0;
        int rightIdx = 0;
        
        while (rightIdx < str.size()) 
        {
            while (rightIdx < str.size() && str[rightIdx] != ' ')
                rightIdx++;
                
            words.push_back(str.substr(leftIdx, rightIdx-leftIdx));
            
            leftIdx  = rightIdx+1;
            rightIdx = rightIdx+1;
        }
        
        if (pattern.size() != words.size())
            return false;
        
        map<char, string> matchTable;
        map<string, char> reverseTable;
        
        for (int i=0; i<pattern.size(); i++) 
        {
            if (matchTable.count(pattern[i]) == 0 && reverseTable.count(words[i]) == 0) 
            {
                matchTable[pattern[i]] = words[i];
                reverseTable[words[i]] = pattern[i];
            } 
            else 
            {
                if (matchTable.count(pattern[i]) != 0 && reverseTable.count(words[i]) != 0)
                {
                    if (words[i] == matchTable[pattern[i]] && pattern[i] == reverseTable[words[i]]) 
                    {
                        continue;
                    }
                }
                return false;
            }
        }
        return true;
    }
};