[LeetCode] 244. Shortest Word Distance II 鏈€鐭崟璇嶈窛绂?II

Posted 2021-01-09

鏍囩锛?a href='http://www.mamicode.com/so/1/%5b%5d' title='[]'>[]   class   post   spl   sign   import   pos   structure   c++   

This is a follow up of Shortest Word Distance. The only difference is now you are given the list of words and your method will be called repeatedly many times with different parameters. How would you optimize it?

Design a class which receives a list of words in the constructor, and implements a method that takes two words word1 and word2 and return the shortest distance between these two words in the list.

For example,
Assume that words = ["practice", "makes", "perfect", "coding", "makes"].

Given word1 = “coding”, word2 = “practice”, return 3.
Given word1 = "makes", word2 = "coding", return 1.

Note:
You may assume that word1 does not equal to word2, and word1 and word2 are both in the list.

243. Shortest Word Distance 鐨勬嫇灞曪紝涓嶅悓鐨勬槸杩欐闇€瑕佸娆¤皟鐢ㄦ眰鏈€鐭崟璇嶈窛绂荤殑鍑芥暟銆?/p>

Python:

# Time:  init: O(n), lookup: O(a + b), a, b is occurences of word1, word2
# Space: O(n)
import collections

class WordDistance:
    # initialize your data structure here.
    # @param {string[]} words
    def __init__(self, words):
        self.wordIndex = collections.defaultdict(list)
        for i in xrange(len(words)):
            self.wordIndex[words[i]].append(i)

    # @param {string} word1
    # @param {string} word2
    # @return {integer}
    # Adds a word into the data structure.
    def shortest(self, word1, word2):
        indexes1 = self.wordIndex[word1]
        indexes2 = self.wordIndex[word2]

        i, j, dist = 0, 0, float("inf")
        while i < len(indexes1) and j < len(indexes2):
            dist = min(dist, abs(indexes1[i] - indexes2[j]))
            if indexes1[i] < indexes2[j]:
                i += 1
            else:
                j += 1

        return dist銆€銆€

C++:

class WordDistance {
public:
    WordDistance(vector<string>& words) {
        for (int i = 0; i < words.size(); ++i) {
            m[words[i]].push_back(i);
        }
    }

    int shortest(string word1, string word2) {
        int res = INT_MAX;
        for (int i = 0; i < m[word1].size(); ++i) {
            for (int j = 0; j < m[word2].size(); ++j) {
                res = min(res, abs(m[word1][i] - m[word2][j]));
            }
        }
        return res;
    }
    
private:
    unordered_map<string, vector<int> > m;
};

C++:

class WordDistance {
public:
    WordDistance(vector<string>& words) {
        for (int i = 0; i < words.size(); ++i) {
            m[words[i]].push_back(i);
        }
    }

    int shortest(string word1, string word2) {
        int i = 0, j = 0, res = INT_MAX;
        while (i < m[word1].size() && j < m[word2].size()) {
            res = min(res, abs(m[word1][i] - m[word2][j]));
            m[word1][i] < m[word2][j] ? ++i : ++j;
        }
        return res;
    }
    
private:
    unordered_map<string, vector<int> > m;
};

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绫讳技棰樼洰锛?/p>

[LeetCode] 243. Shortest Word Distance 鏈€鐭崟璇嶈窛绂?/a>

[LeetCode] 245. Shortest Word Distance III 鏈€鐭崟璇嶈窛绂?III