Leetcode 290. Word Pattern

290. Word Pattern

Total Accepted: 42115 Total Submissions: 140014 Difficulty: 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.

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.

思路：映射。详细可以参考Leetcode 205. Isomorphic Strings的第一个方法

代码：

注意istringstream的用法，头文件<sstream>。这个可以专门用来分解含空格的字符串。

class Solution {
public:
    bool wordPattern(string pattern, string str) {
        map<char,int> p2i;
        map<string,int> s2i;
        string temp;
        int i=0,n=pattern.size();
        istringstream in(str);
        while(in>>temp){
            if(i<n){
                //map中没有对应的键-值对，则返回0
                if(p2i[pattern[i]]!=s2i[temp]){
                    return false;
                }
                p2i[pattern[i]]=s2i[temp]=i+1;
            }
            i++;
        }
        return i==n;
    }
};