Leetcode NO.290 Word Pattern

本题题目要求如下：

Given a 

pattern

 and a string 

str

,
find if 

str

 follows the same pattern.

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:

pattern

contains only lowercase alphabetical letters, and 

str

 contains
words separated by a single space. Each word in 

str

 contains only lowercase alphabetical
letters.
Both 

pattern

 and 

str

 do
not have leading or trailing spaces.
Each letter in 

pattern

 must map to a word with length that is at least 1.

本题应该算是easy中的easy了，思路相当直接，就是用hashmap，当然需要注意一点就是不光要避免'a'->"dog"和'a'->"cat"这种冲突，还要解决'a'->"dog"和'b'->dog这种冲突。。我的解决方法是加一个hashset，也许有更好地，但是这么做也行。。
代码如下：

class Solution {
public:
bool wordPattern(string pattern, string str) {
istringstream is(str);
unordered_map<char, string> hashmap;
unordered_set<string> hashset;
string word;
int sz = pattern.length();
int i = 0;
while (is >> word) {
hashset.insert(word);
if (i == sz) {
return false;
}
char tmp_val = pattern[i++];
auto found = hashmap.find(tmp_val);
if (found == hashmap.end()) {
hashmap[tmp_val] = word;
}
else {
if (hashmap[tmp_val] != word) {
return false;
}
}
}
return (hashset.size() == hashmap.size() and i == sz);
}
};