Find Common Characters

Description

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.

Code

Time Complexity: $O(n)$, Space Complexity: $O(1)$

class Solution {
public:
    vector<string> commonChars(vector<string>& words) {
        vector<int> count(26, INT_MAX);
        for(int i = 0; i < words.size(); i++) {
            vector<int> count2(26, 0);
            for(auto c: words[i]) {
                count2[c - 'a']++;
            }
            for(int i = 0; i < 26; i++) {
                count[i] = min(count[i], count2[i]);
            }
        }
 
        vector<string> res;
        for(int i = 0; i < 26; i++) {
            for(int k = 0; k < count[i]; k++)
                res.push_back(string(1, (i + 'a')));
        }
        return res;
    }
};

Source

• Find Common Characters - LeetCode