[leetcode] Word Pattern

注意一一对应即可：

class Solution {public:    bool wordPattern(string pattern, string str) {        int i = -1, pos = 0;        unordered_map<string, char> mp;        unordered_set<char> st;        while(++i < pattern.length() && pos != string::npos) {            string s;            int nPos = str.find(' ', pos);            if(nPos != string::npos) s = str.substr(pos, nPos - pos);            else s = str.substr(pos);            if(mp.find(s) == mp.end()) {                if(st.find(pattern[i]) != st.end())                    return false;                mp[s] = pattern[i];                st.insert(pattern[i]);            }            if(i != 0 && mp[s] != pattern[i])                return false;            if(nPos == string::npos) {                pos = nPos;                break;            }            pos = nPos + 1;        }        if(i != pattern.length() - 1 || pos != string::npos)            return false;        return true;    }};