LeetCode 290. Word Pattern

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#Word Pattern #LeetCode #哈希表

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本文介绍了一种模式匹配算法，该算法通过使用两个哈希表来确保输入的模式与字符串完全匹配。具体实现上，通过对比模式串与单词串中每个元素的一一对应关系，实现了模式与字符串之间的双射映射。

Word Pattern

题目描述:

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.

题目思路:

用两个哈希表，将两个字符串的对应位置给予相同的映射，如果已有映射不相同，则返回false

题目代码:

class Solution {
public:
    bool wordPattern(string pattern, string str) {
        istringstream in(str);
        map<string,int>table1;
        map<char, int>table2;
        int i = 0, n = pattern.length();
        for(string word; in >> word; i++){
            if(table2[pattern[i]] != table1[word] || i==n){
                return false;
            }else{
                table1[word] = table2[pattern[i]] = i+1;
            }
        }
        return i==n;
    }
};