748. Shortest Completing Word*-CFANZ编程社区

748. Shortest Completing Word*

https://leetcode.com/problems/shortest-completing-word/

题目描述

Find the minimum length word from a given dictionary words, which has all the letters from the string licensePlate. Such a word is said to complete the given string licensePlate.

Here, for letters we ignore case. For example, "P" on the licensePlate still matches "p" on the word.

It is guaranteed an answer exists. If there are multiple answers, return the one that occurs first in the array.

The license plate might have the same letter occurring multiple times. For example, given a licensePlate of "PP", the word "pair" does not complete the licensePlate, but the word "supper" does.

Example 1:

Input: licensePlate = "1s3 PSt", words = ["step", "steps", "stripe", "stepple"]
Output: "steps"
Explanation: The smallest length word that contains the letters "S", "P", "S", and "T".
Note that the answer is not "step", because the letter "s" must occur in the word twice.
Also note that we ignored case for the purposes of comparing whether a letter exists in the word.

Example 2:

Input: licensePlate = "1s3 456", words = ["looks", "pest", "stew", "show"]
Output: "pest"
Explanation: There are 3 smallest length words that contains the letters "s".
We return the one that occurred first.

Note:

licensePlate will be a string with length in range[1, 7].
licensePlate will contain digits, spaces, or letters (uppercase or lowercase).
words will have a length in the range[10, 1000].
Everywords[i] will consist of lowercase letters, and have length in range[1, 15].

C++ 实现 1

这题原本不难, 但题意有时让人困惑, 比如:

For example, given a licensePlate of "PP", the word "pair" does not complete the licensePlate, but the word "supper" does.

这句描述会让人以为 word = 'supeper' 这种单词不符合要求, 但实际上是符合的, 只要 word 包含 licensePlate 中的所有字符, 并且个数也包含即可.

另外要注意最后返回字符长度最短的 word.

class Solution {
private:
    bool matches(string &word, unordered_map<char, int> &plate) {
        // 判断 word 中是否包含 plate 中的所有字符以及对应的个数
        unordered_map<char, int> record;
        for (auto &c : word)
            record[c] ++;
        
        for (auto &iter : plate) {
            if (!record.count(iter.first) ||
                (record.count(iter.first) && record[iter.first] < iter.second))
                return false; 
        }
        return true;
    }
public:
    string shortestCompletingWord(string licensePlate, vector<string>& words) {
        // 统计 licensePlate 中的字符个数
        unordered_map<char, int> plate;
        for (auto &c : licensePlate)
            if (isalpha(c))
                plate[tolower(c)] ++;
        
        string res;
        int len = INT32_MAX;
        for (auto &word : words) {
            // 找到长度最短的 word.
            if (matches(word, plate) && word.size() < len) {
                res = word;
                len = word.size();
            }
        }
        return res;
    }
};