290. 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:

1. pattern = "abba", str = "dog cat cat dog" should return true.
2. pattern = "abba", str = "dog cat cat fish" should return false.
3. pattern = "aaaa", str = "dog cat cat dog" should return false.
4. 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.

Credits:

Special thanks to @minglotus6 for adding this problem and creating all test cases.

该题目思路和205题Isomorphic Strings 几乎完全一样，只不过变成了字符和string的映射罢了。

class Solution {public:    bool wordPattern(string pattern, string str) {        map<char,string>mp1;        map<string,char>mp2;        vector<string> vec;        int len=str.size();//求字符串的长度这种函数最好还是放在FOR循环的外面，不然每次循环都要求一次长度，可能会导致超时        for(int i=0,j=0;i<len;i++){            if(str[i]==' '){                vec.push_back(str.substr(j,i-j));                j=i+1;            }            else if(i==len-1){                vec.push_back(str.substr(j,i-j+1));            }        }        if(pattern.size()!=vec.size())return false;        for(int i=0;i<vec.size();i++){            if(mp1.find(pattern[i])==mp1.end()&&mp2.find(vec[i])==mp2.end()){                mp1[pattern[i]]=vec[i];                mp2[vec[i]]=pattern[i];            }            else if(mp1[pattern[i]]!=vec[i]||mp2[vec[i]]!=pattern[i])                return false;        }        return true;    }};