README_EN.md

290. Word Pattern

中文文档

Description

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.

Solutions

Python3

class Solution:
    def wordPattern(self, pattern: str, s: str) -> bool:
        s = s.split(' ')
        n = len(pattern)
        if n != len(s):
            return False
        c2str, str2c = defaultdict(), defaultdict()
        for i in range(n):
            k, v = pattern[i], s[i]
            if k in c2str and c2str[k] != v:
                return False
            if v in str2c and str2c[v] != k:
                return False
            c2str[k], str2c[v] = v, k
        return True

Java

class Solution {
    public boolean wordPattern(String pattern, String s) {
        String[] ss = s.split(" ");
        int n = pattern.length();
        if (n != ss.length) {
            return false;
        }
        Map<Character, String> c2str = new HashMap<>();
        Map<String, Character> str2c = new HashMap<>();
        for (int i = 0; i < n; ++i) {
            char k = pattern.charAt(i);
            String v = ss[i];
            if (c2str.containsKey(k) && !Objects.equals(c2str.get(k), v)) {
                return false;
            }
            if (str2c.containsKey(v) && !Objects.equals(str2c.get(v), k)) {
                return false;
            }
            c2str.put(k, v);
            str2c.put(v, k);
        }
        return true;
    }
}

TypeScript

function wordPattern(pattern: string, s: string): boolean {
    let n = pattern.length;
    let values = s.split(' ');
    if (n != values.length) return false;
    let table = new Array(128);
    for (let i = 0; i < n; i++) {
        let k = pattern.charCodeAt(i),
            v = values[i];
        if (!table[k]) {
            if (table.includes(v)) return false;
            table[k] = v;
        } else {
            if (table[k] != v) return false;
        }
    }
    return true;
}

C++

class Solution {
public:
    bool wordPattern(string pattern, string s) {
        istringstream is(s);
        vector<string> ss;
        while (is >> s) ss.push_back(s);
        int n = pattern.size();
        if (n != ss.size()) return false;

        unordered_map<char, string> c2str;
        unordered_map<string, char> str2c;
        for (int i = 0; i < n; ++i)
        {
            char k = pattern[i];
            string v = ss[i];
            if (c2str.count(k) && c2str[k] != v) return false;
            if (str2c.count(v) && str2c[v] != k) return false;
            c2str[k] = v;
            str2c[v] = k;
        }
        return true;
    }
};

Go

func wordPattern(pattern string, s string) bool {
	ss := strings.Split(s, " ")
	n := len(pattern)
	if n != len(ss) {
		return false
	}
	c2str := make(map[byte]string)
	str2c := make(map[string]byte)
	for i := 0; i < n; i++ {
		k, v := pattern[i], ss[i]
		if c2str[k] != "" && c2str[k] != v {
			return false
		}
		if str2c[v] > 0 && str2c[v] != k {
			return false
		}
		c2str[k], str2c[v] = v, k
	}
	return true
}

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