LeetCode290. Word Pattern

一、题目

Given a pattern and a string s, find if s 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 s.

Example 1:

Input: pattern = “abba”, s = “dog cat cat dog”
Output: true
Example 2:

Input: pattern = “abba”, s = “dog cat cat fish”
Output: false
Example 3:

Input: pattern = “aaaa”, s = “dog cat cat dog”
Output: false

Constraints:

1 <= pattern.length <= 300
pattern contains only lower-case English letters.
1 <= s.length <= 3000
s contains only lowercase English letters and spaces ’ '.
s does not contain any leading or trailing spaces.
All the words in s are separated by a single space.

二、题解

判断一一对应：用两个哈希表

class Solution {
public:
    bool wordPattern(string pattern, string s) {
        unordered_map<char,string> map1;
        unordered_map<string,char> map2;
        istringstream iss(s);
        vector<string> tmp;
        string str;
        while(iss >> str) tmp.push_back(str);
        if(tmp.size() != pattern.size()) return false;
        for(int i = 0;i < pattern.size();i++){
            if(map1.find(pattern[i]) == map1.end()) map1[pattern[i]] = tmp[i];
            else{
                if(map1[pattern[i]] != tmp[i]) return false;
            }
            if(map2.find(tmp[i]) == map2.end()) map2[tmp[i]] = pattern[i];
            else {
                if(map2[tmp[i]] != pattern[i]) return false;
            }
        }
        return true;
    }
};