/*

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.

*/

class Solution {

public:

bool wordPattern(string pattern, string str) {

int p2i[26] {}; //C++11 set p2i 0

unordered_map<string, int> w2i;

istringstream in(str); //seperate the str with space

int i = 0, n = pattern.size();

for (string word; in >> word ; ++i) {

if (i == n || p2i[pattern[i] - 'a'] != w2i[word])

return false;

p2i[pattern[i] - 'a'] = w2i[word] = i + 1; //record the position

}

return i == n;

}

};