290. Word Pattern

1.描述

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.

2.分析

3.代码

class Solution {
public:
    bool wordPattern(string pattern, string str) {
        map p2i;
        map w2i;
        istringstream iss(str);
        int i = 0, n = pattern.size();
        for (string word; iss >> word; i++) {
            if (i == n || p2i[pattern[i]] != w2i[word]) {
                return false;
            }
            p2i[pattern[i]] = w2i[word] = i + 1;
        }
        return i == n;
    }
};