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:

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.

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();
}
};