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:
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.

s思路:
1. 由于是一一映射，所以需要两个hash分别负责从pattern->str，str->pattern的映射
2. 另外需要take care of the length consistence. In other words, the two should have the same length.

//方法１：hashclass Solution {public:    bool wordPattern(string pattern, string str) {        //        int n=str.size();        unordered_map<string,string> mm1,mm2;        int count=0;        for(int i=0;i<str.size();i++){            if(count>=n) return false;            if(str[i]==' '){                count++;                continue;            }            int j=i;            while(j<str.size()&&str[j]!=' '){                j++;                }               string cur=str.substr(i,j-i);            string p=pattern.substr(count,1);            if(mm1.count(cur)&&mm2.count(p)){                if(mm1[cur]!=p&&mm2[p]!=cur) return false;            }else if((mm1.count(cur)==0)&&(mm2.count(p)==0)){                mm1[cur]=p;                mm2[p]=cur;             }else                return false;            i=j-1;        }        return count==pattern.size()-1;    }};