LeetCode 290 Word Pattern

题目描述

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:

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.

Credits:
Special thanks to @minglotus6 for adding this problem and creating all test cases.

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分析

保证1对1的映射关系

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代码

    public boolean wordPattern(String pattern, String str) {        if (pattern == null || str == null) {            return false;        }        String[] strs = str.split(" ");        if (pattern.length() != strs.length) {            return false;        }        Map<Character, String> map = new HashMap<Character, String>();        for (int i = 0; i < pattern.length(); i++) {            char c = pattern.charAt(i);            if (map.containsKey(c)) {                if (!map.get(c).equals(strs[i])) {                    return false;                }            } else {                // 保证1对1的映射                if (map.containsValue(strs[i])) {                    return false;                }                map.put(c, strs[i]);            }        }        return true;    }