LeetCode-in-Java

1002. Find Common Characters

Easy

Given a string array words, return an array of all characters that show up in all strings within the words (including duplicates). You may return the answer in any order.

Example 1:

Input: words = [“bella”,”label”,”roller”]

Output: [“e”,”l”,”l”]

Example 2:

Input: words = [“cool”,”lock”,”cook”]

Output: [“c”,”o”]

Constraints:

• 1 <= words.length <= 100
• 1 <= words[i].length <= 100
• words[i] consists of lowercase English letters.

Solution

import java.util.ArrayList;
import java.util.List;

@SuppressWarnings("java:S112")
public class Solution {
    public List<String> commonChars(String[] words) {
        if (words == null) {
            throw new RuntimeException("words null");
        }
        if (words.length == 0) {
            return new ArrayList<>();
        }
        String tmp = words[0];
        for (int i = 1; i < words.length; i++) {
            tmp = getCommon(tmp, words[i]);
        }
        List<String> result = new ArrayList<>();
        for (int i = 0; i < tmp.length(); i++) {
            result.add(String.valueOf(tmp.charAt(i)));
        }
        return result;
    }

    private String getCommon(String s1, String s2) {
        if (s1.length() == 0 || s2.length() == 0) {
            return "";
        }
        int[] c1c = countChars(s1);
        int[] c2c = countChars(s2);
        StringBuilder sb = new StringBuilder();
        for (int i = 0; i < c1c.length; i++) {
            int m = Math.min(c1c[i], c2c[i]);
            while (m > 0) {
                sb.append((char) ('a' + i));
                m--;
            }
        }
        return sb.toString();
    }

    private int[] countChars(String str) {
        int[] result = new int[26];
        for (int i = 0; i < str.length(); i++) {
            result[str.charAt(i) - 'a']++;
        }
        return result;
    }
}

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