LeetCode 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.

    题目的大致意思是：给两个字符串，其中一个表示轨迹，检查第二个字符串是否符合第一个轨迹而存在，如果两者轨迹相同返回true，不同则返回false。 其中注意:pattern="aaaa",str="aa aa aa aa aa aa"两者轨迹并不相同

class Solution {
public:
    bool wordPattern(string pattern, string str) {
        auto beg = begin(str), en = end(str);
        string::iterator mid=beg;
        map<char, string> ma;
        for (unsigned i = 0;i < pattern.size();++i)
        {
            for (;mid != en && ((*mid) != ' ');++mid);
            if(ma.find(pattern[i])==ma.end())
            ma[pattern[i]] = string(beg, mid);
            if (ma.find(pattern[i]) != ma.end() && ma[pattern[i]] != string(beg, mid))
                return false;
            if(mid!=en)
            beg = ++mid;
        }
        map<string, char> test;
        for (auto e : ma)
            test[e.second] = e.first;
        if (ma.size( )!= test.size()||mid!=en)
            return false;
        return true;
    }
};