Word Pattern -- Leetcode

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.

题目可以理解为

存在两个集合，找出集合元素之间的是否存在一一对应的映射关系。

class Solution {public:    bool wordPattern(string pattern, string str) {        map<string, int> map_p;        map<string, int> map_s;        istringstream in(str);        int i = 0;        for (string word_s; pattern.size() && in >> word_s ; ++i) {            const string word_p(1, pattern[i]);            if (map_s[word_s] != map_p[word_p])                return false;                            map_p[word_p] = map_s[word_s] = i + 1;        }                return i == pattern.size() && in.eof();    }};