LeetCode 734. Sentence Similarity



We can represent a sentence as an array of words, for example, the sentence "I am happy with leetcode" can be represented as arr = ["I","am",happy","with","leetcode"].

Given two sentences sentence1 and sentence2 each represented as a string array and given an array of string pairs similarPairs where similarPairs[i] = [xi, yi] indicates that the two words xi and yi are similar.

Return true if sentence1 and sentence2 are similar, or false if they are not similar.

Two sentences are similar if:

  • They have the same length (i.e. the same number of words)
  • sentence1[i] and sentence2[i] are similar.

Notice that a word is always similar to itself, also notice that the similarity relation is not transitive. For example, if the words a and b are similar and the words b and c are similar, a and c are not necessarily similar.

Example 1:

Input: sentence1 = ["great","acting","skills"], sentence2 = ["fine","drama","talent"], similarPairs = [["great","fine"],["drama","acting"],["skills","talent"]]
Output: true
Explanation: The two sentences have the same length and each word i of sentence1 is also similar to the corresponding word in sentence2.

Example 2:

Input: sentence1 = ["great"], sentence2 = ["great"], similarPairs = []
Output: true
Explanation: A word is similar to itself.

Example 3:

Input: sentence1 = ["great"], sentence2 = ["doubleplus","good"], similarPairs = [["great","doubleplus"]]
Output: false
Explanation: As they don't have the same length, we return false.


  • 1 <= sentence1.length, sentence2.length <= 1000
  • 1 <= sentence1[i].length, sentence2[i].length <= 20
  • sentence1[i] and sentence2[i] consist of lower-case and upper-case English letters.
  • 0 <= similarPairs.length <= 1000
  • similarPairs[i].length == 2
  • 1 <= xi.length, yi.length <= 20
  • xi and yi consist of lower-case and upper-case English letters.
  • All the pairs (xi,yi) are distinct.


First compare the length of two sentences. Then check if words in sequences are in pairs.

Python Solution

class Solution:
    def areSentencesSimilar(self, sentence1: List[str], sentence2: List[str], similarPairs: List[List[str]]) -> bool:
        if len(sentence1) != len(sentence2):
            return False
        pairs_dict = defaultdict(set)
        for pair in similarPairs:
        for word1, word2 in zip(sentence1, sentence2):
            if word1 != word2 and word2 not in pairs_dict[word1]:           
                return False
        return True
  • Time Complexity: O(N).
  • Space Complexity: O(N).

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