[leetcode]748. Shortest Completing Word能覆盖车牌最短单词

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:

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

题意：

给你一个由字母和数字组成车牌。另外给你一些单词，让你找一个最短的单词能够覆盖住车牌中的字母（不考虑大小写）。如果有多个解，输出第一个解。

Solution:  HashMap 

code

class Solution {
    public String shortestCompletingWord(String licensePlate, String[] words) {
           // scan each char of licensePlate
        int[] mapP = new int[256];
        int count = 0;
        int minLen = Integer.MAX_VALUE;
        String result = " ";
        for(int i = 0; i < licensePlate.length(); i++){
            char c = licensePlate.charAt(i);
            if(Character.isLetter(c)){
                mapP[Character.toLowerCase(c)]++;
                count ++;
            }
        }
        
        for(String s : words){
            int markCount = count;
            int [] mapS = new int[256];
            for(int i = 0; i < s.length(); i++){
                char c = s.charAt(i);
                mapS[c]++;
                if(mapP[c] >= mapS[c]){
                    markCount--;
                    if(markCount == 0 && s.length() < minLen){
                        minLen = s.length();
                        result = s;
                    }
                }
            }
        }
        return result;
    }
}