290. Word Pattern--Easy

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.

Example 1:

Input: pattern = "abba", str = "dog cat cat dog"
Output: true
Example 2:

Input:pattern = "abba", str = "dog cat cat fish"
Output: false
Example 3:

Input: pattern = "aaaa", str = "dog cat cat dog"
Output: false
Example 4:

Input: pattern = "abba", str = "dog dog dog dog"
Output: false
Notes:
You may assume pattern contains only lowercase letters, and str contains lowercase letters that may be separated by a single space.

1.思考

• 首先将string str中的元素以空格为分界按顺序取出存放于vector中；
• 再通过二重循环，将pattern中两两组队，并对比str中相同位置的元素是否相同；
• 若pattern中相同，而str中不同，则return false；
• 若pattern中不同，而str中相同，则return false；
• 若遍历所有都没有返回值，则return true。
  
  

2.实现
Runtime: 0ms(100%)
Memory: 9MB(6.09%)

class Solution {
public:
    bool wordPattern(string pattern, string str) {        
        int len = pattern.size();
        vector<string> st;
        
        int ln = str.size();
        string s = str;
        while(1){
            int pos = s.find(' ');
            if(pos>0){                
                st.push_back(s.substr(0, pos));
                s = s.substr(pos+1);
            }
            else{
                st.push_back(s);
                break;
            }
        }
        
        if(st.size() != len)
            return false;
        
        for(int i=0; i<len; i++){            
            for(int j=i+1; j<len; j++){
                if(pattern[i] == pattern[j]){
                    if(st[i] != st[j]){
                        return false;
                    }
                }
                else{
                    if(st[i] == st[j]){
                        return false;
                    }                    
                }
            }            
        }
        
        return true;        
        
    }
};