LeetCode 290. Word Pattern

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本文介绍了一种用于判断字符串str是否遵循给定模式pattern的算法。该算法通过建立字符到单词的映射关系来实现模式匹配，并提供了具体的实现代码示例。

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.

分析：

具体的做法和思路和205. Isomorphic Strings类似，只需要将str依据space分段，然后存放在数组中。

class Solution {
public:
    bool wordPattern(string pattern, string str) {
        map<char,string>m1;
        map<string,char>m2;
        int n=str.length(),r=0;
        vector<string> c(n);
        string s="";
        for(int i=0;i<n;i++){
            if(str[i]==' '){
                c[r++]=s;
                s="";
            }else{
                s=s+str[i];
            }   
        }
        c[r++]=s;//将最后一个添加
        if(r!=pattern.length()) return false;
        for(int i=0;i<pattern.length();i++){
            if(m1.count(pattern[i])>0&&m1[pattern[i]]!=c[i]||m2.count(c[i])&&m2[c[i]]!=pattern[i]) return false;
            m1[pattern[i]]=c[i];
            m2[c[i]]=pattern[i];
        }
        return true;
    }
};